diff --git a/.github/workflows/mariadb-test.yml b/.github/workflows/mariadb-test.yml
index d693e86..fd516ce 100644
--- a/.github/workflows/mariadb-test.yml
+++ b/.github/workflows/mariadb-test.yml
@@ -99,7 +99,6 @@ jobs:
       uses: actions/cache@v4
       with:
         path: |
-          tidesdb-lib/build
           /usr/local/lib/libtidesdb*
           /usr/local/include/tidesdb*
           C:/tidesdb
@@ -149,24 +148,12 @@ jobs:
         echo "CMAKE_TOOLCHAIN_FILE=$env:VCPKG_INSTALLATION_ROOT/scripts/buildsystems/vcpkg.cmake" >> $env:GITHUB_ENV
         echo "TIDESDB_ROOT=C:/tidesdb" >> $env:GITHUB_ENV
 
-    - name: Get latest MariaDB release tag
+    - name: Set MariaDB version
       id: mariadb-release
       shell: bash
-      env:
-        GH_TOKEN: ${{ github.token }}
       run: |
-        for i in 1 2 3; do
-          LATEST_TAG=$(curl -s -H "Authorization: Bearer $GH_TOKEN" https://api.github.com/repos/MariaDB/server/releases/latest | jq -r '.tag_name')
-          if [ -n "$LATEST_TAG" ] && [ "$LATEST_TAG" != "null" ]; then
-            echo "tag=${LATEST_TAG}" >> $GITHUB_OUTPUT
-            echo "Latest MariaDB release: ${LATEST_TAG}"
-            exit 0
-          fi
-          echo "Attempt $i: Failed to get tag (got: $LATEST_TAG), retrying in 5s..."
-          sleep 5
-        done
-        echo "Failed to get MariaDB release tag after 3 attempts, using fallback"
-        echo "tag=mariadb-12.2.2" >> $GITHUB_OUTPUT
+        echo "tag=mariadb-12.1.2" >> $GITHUB_OUTPUT
+        echo "MariaDB version: mariadb-12.1.2"
 
     - name: Clone MariaDB server
       shell: bash
@@ -189,6 +176,7 @@ jobs:
     - name: Install TidesDB library (Ubuntu)
       if: runner.os == 'Linux'
       run: |
+        rm -rf tidesdb-lib
         for i in 1 2 3; do
           if git clone --depth 1 https://github.com/tidesdb/tidesdb.git tidesdb-lib; then
             break
@@ -212,6 +200,7 @@ jobs:
         sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
         export SDKROOT=$(xcrun --show-sdk-path)
         
+        rm -rf tidesdb-lib
         for i in 1 2 3; do
           if git clone --depth 1 https://github.com/tidesdb/tidesdb.git tidesdb-lib; then
             break
@@ -232,6 +221,7 @@ jobs:
       if: runner.os == 'Windows'
       shell: bash
       run: |
+        rm -rf tidesdb-lib
         for i in 1 2 3; do
           if git clone --depth 1 https://github.com/tidesdb/tidesdb.git tidesdb-lib; then
             break
@@ -281,7 +271,6 @@ jobs:
           -DPLUGIN_COLUMNSTORE=NO \
           -DPLUGIN_CONNECT=NO \
           -DPLUGIN_OQGRAPH=NO \
-          -DPLUGIN_TOKUDB=NO \
           -DPLUGIN_ARCHIVE=NO \
           -DWITH_UNIT_TESTS=OFF \
           -DCONC_WITH_UNITTEST=OFF \
@@ -321,7 +310,6 @@ jobs:
           -DPLUGIN_SPIDER=NO \
           -DPLUGIN_ROCKSDB=NO \
           -DPLUGIN_OQGRAPH=NO \
-          -DPLUGIN_TOKUDB=NO \
           -DPLUGIN_COLUMNSTORE=NO \
           -DWITH_UNIT_TESTS=OFF \
           -DCONC_WITH_UNITTEST=OFF \
@@ -342,7 +330,7 @@ jobs:
       run: |
         mkdir build
         cd build
-        cmake .. -G "Visual Studio 17 2022" -A x64 -DPLUGIN_TIDESDB=DYNAMIC -DPLUGIN_ROCKSDB=NO -DPLUGIN_MROONGA=NO -DPLUGIN_SPIDER=NO -DPLUGIN_COLUMNSTORE=NO -DPLUGIN_CONNECT=NO -DWITH_UNIT_TESTS=OFF -DCMAKE_PREFIX_PATH="C:/tidesdb;%VCPKG_INSTALLATION_ROOT%/installed/x64-windows" -DCMAKE_INCLUDE_PATH="C:/tidesdb/include"
+        cmake .. -G "Visual Studio 17 2022" -A x64 -DPLUGIN_TIDESDB=DYNAMIC -DPLUGIN_ROCKSDB=NO -DPLUGIN_MROONGA=NO -DPLUGIN_SPIDER=NO -DPLUGIN_COLUMNSTORE=NO -DPLUGIN_CONNECT=NO -DPLUGIN_OQGRAPH=NO -DPLUGIN_ARCHIVE=NO -DWITH_UNIT_TESTS=OFF -DCMAKE_PREFIX_PATH="C:/tidesdb;%VCPKG_INSTALLATION_ROOT%/installed/x64-windows" -DCMAKE_INCLUDE_PATH="C:/tidesdb/include"
         cmake --build . --config RelWithDebInfo --parallel
 
     - name: Run TidesDB test suite (Linux)
diff --git a/README b/README
index feb1a65..e88a908 100644
--- a/README
+++ b/README
@@ -3,6 +3,8 @@ TIDESQL
 
 A pluggable write and space optimized storage engine for MariaDB using TidesDB.
 
+The pluggable engine is tested and supported on MariaDB 11.x, 12.x.
+
 
 INSTALLATION
 ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
@@ -17,12 +19,34 @@ The install script will build TidesDB and MariaDB from source.
 You can specify the versions if you want.  The script will install everything
 and make TidesDB available as an engine to utilize.
 
+To skip storage engines you don't need (saves build time and reduces warnings):
+
+./install.sh --list-engines                       # see what can be skipped
+./install.sh --skip-engines mroonga,rocksdb,connect,spider,oqgraph,columnstore
+
+Skippable engines:
+  archive        Archive storage engine (read-only row-format tables)
+  blackhole      Blackhole engine (accepts writes, stores nothing)
+  columnstore    MariaDB ColumnStore (columnar analytics engine)
+  connect        CONNECT engine (access external data sources)
+  example        Example storage engine (test/demo only)
+  federated      Legacy Federated engine (MODULE_ONLY)
+  federatedx     FederatedX engine (query remote MySQL/MariaDB tables)
+  mroonga        Mroonga full-text search engine (requires Groonga)
+  oqgraph        Open Query GRAPH engine (graph computation)
+  rocksdb        MyRocks / RocksDB LSM-tree engine
+  sequence       Sequence engine (virtual auto-increment sequences)
+  sphinx         SphinxSE engine (Sphinx full-text search integration)
+  spider         Spider engine (sharding / federation)
+
+InnoDB, Aria, MyISAM, and CSV cannot be skipped (server depends on them).
+
 Below are manual install instructions for those who want to configure everything
 themselves, though with the install script you can modify configuration files
 after the fact.
 
 LINUX (Ubuntu/Debian)
----------------------
+░░░░░░░░░░░░░░░░░░░░░░░░
 
 1. Install dependencies:
 
@@ -61,7 +85,7 @@ LINUX (Ubuntu/Debian)
 
 
 MACOS
------
+░░░░░░░░░░░░░░░░░░░░░░░░
 
 1. Install dependencies:
 
@@ -119,7 +143,7 @@ MACOS
 
 
 WINDOWS
--------
+░░░░░░░░░░░░░░░░░░░░░░░░
 
 1. Install prerequisites:
 
@@ -171,7 +195,7 @@ WINDOWS
 
 
 ENABLE PLUGIN
--------------
+░░░░░░░░░░░░░░░░░░░░░░░░
 
 After building, enable the plugin in MariaDB:
 
@@ -213,7 +237,7 @@ TidesDB stores its data as a sibling of the MariaDB data directory:
 
 
 SYSTEM VARIABLES (SET GLOBAL tidesdb_...)
------------------------------------------
+░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
 
 All are read-only (set at startup) unless noted otherwise.
 
@@ -232,7 +256,7 @@ reduce log volume.
 
 
 TABLE OPTIONS (CREATE TABLE ... ENGINE=TidesDB <option>=<value>)
-----------------------------------------------------------------
+░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
 
 These are per-table options baked into the column family at creation time.
 Changing them via ALTER TABLE only updates the .frm; it does not reconfigure
@@ -284,7 +308,7 @@ Encryption:
 
 
 FIELD OPTIONS (per-column)
---------------------------
+░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
 
   TTL                       Marks column as per-row TTL source (seconds)
 
@@ -326,6 +350,7 @@ Available tests:
   tidesdb_json            JSON querying + generated-column JSON path indexing
   tidesdb_savepoint       SQL SAVEPOINT / ROLLBACK TO / RELEASE SAVEPOINT
   tidesdb_write_pressure  oltp_write_only OOM reproduction (multi-connection)
+  ...
 
 Run with verbose output:
 
diff --git a/install.sh b/install.sh
index 6e3a971..64d5d6c 100755
--- a/install.sh
+++ b/install.sh
@@ -48,6 +48,8 @@
 #   --jobs            N         Parallel build jobs        (default: auto-detected)
 #   --skip-deps                 Skip system dependency installation
 #   --skip-tidesdb              Skip TidesDB library build (use if already installed)
+#   --skip-engines  ENGINES     Comma-separated list of storage engines to skip
+#   --list-engines              List storage engines that can be skipped and exit
 #   --pgo                       Enable Profile-Guided Optimization (3-phase build)
 #   --help                      Show this help message
 #
@@ -68,6 +70,8 @@
 #   ./install.sh --mariadb-version mariadb-12.1.2
 #   ./install.sh --skip-deps --skip-tidesdb
 #   ./install.sh --pgo          # Full PGO build (instrument → train → optimize)
+#   ./install.sh --list-engines # Show which engines can be skipped
+#   ./install.sh --skip-engines mroonga,rocksdb,connect,spider,oqgraph,columnstore
 # ─────────────────────────────────────────────────────────────────────────────
 set -euo pipefail
 
@@ -160,6 +164,27 @@ JOBS="$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 4)"
 SKIP_DEPS=false
 SKIP_TIDESDB=false
 PGO_ENABLED=false
+SKIP_ENGINES=""
+
+# ── Skippable storage engines ────────────────────────────────────────────────
+# These are MariaDB storage engines that can safely be disabled to save build
+# time and reduce compiler warnings.  InnoDB, Aria, MyISAM, and CSV are NOT
+# listed here because the server or mysql-test framework depends on them.
+SKIPPABLE_ENGINES=(
+    "archive:Archive storage engine (read-only row-format tables)"
+    "blackhole:Blackhole engine (accepts writes, stores nothing)"
+    "columnstore:MariaDB ColumnStore (columnar analytics engine)"
+    "connect:CONNECT engine (access external data sources)"
+    "example:Example storage engine (test/demo only)"
+    "federated:Legacy Federated engine (MODULE_ONLY)"
+    "federatedx:FederatedX engine (query remote MySQL/MariaDB tables)"
+    "mroonga:Mroonga full-text search engine (requires Groonga)"
+    "oqgraph:Open Query GRAPH engine (graph computation)"
+    "rocksdb:MyRocks / RocksDB LSM-tree engine"
+    "sequence:Sequence engine (virtual auto-increment sequences)"
+    "sphinx:SphinxSE engine (Sphinx full-text search integration)"
+    "spider:Spider engine (sharding / federation)"
+)
 
 # ── Color helpers ───────────────────────────────────────────────────────────
 RED='\033[0;31m'
@@ -180,6 +205,21 @@ usage() {
     exit 0
 }
 
+list_engines() {
+    echo ""
+    echo -e "${CYAN}Skippable storage engines:${NC}"
+    echo -e "${CYAN}──────────────────────────────────────────────────────────${NC}"
+    for entry in "${SKIPPABLE_ENGINES[@]}"; do
+        local name="${entry%%:*}"
+        local desc="${entry#*:}"
+        printf "  ${GREEN}%-14s${NC} %s\n" "$name" "$desc"
+    done
+    echo ""
+    echo -e "Usage: ${GREEN}--skip-engines mroonga,rocksdb,connect${NC}"
+    echo ""
+    exit 0
+}
+
 while [[ $# -gt 0 ]]; do
     case "$1" in
         --tidesdb-version)  TIDESDB_VERSION="$2";  shift 2 ;;
@@ -190,6 +230,8 @@ while [[ $# -gt 0 ]]; do
         --jobs)             JOBS="$2";              shift 2 ;;
         --skip-deps)        SKIP_DEPS=true;         shift   ;;
         --skip-tidesdb)     SKIP_TIDESDB=true;      shift   ;;
+        --skip-engines)     SKIP_ENGINES="$2";      shift 2 ;;
+        --list-engines)     list_engines ;;
         --pgo)              PGO_ENABLED=true;       shift   ;;
         --help|-h)          usage ;;
         *) die "Unknown option: $1 (try --help)" ;;
@@ -229,6 +271,9 @@ _cfg_row "Build directory  : ${GREEN}${BUILD_DIR}${NC}"
 _cfg_row "Parallel jobs    : ${GREEN}${JOBS}${NC}"
 _cfg_row "Detected OS      : ${GREEN}${OS}${NC}"
 _cfg_row "PGO build        : ${GREEN}${PGO_ENABLED}${NC}"
+if [[ -n "$SKIP_ENGINES" ]]; then
+_cfg_row "Skip engines     : ${YELLOW}${SKIP_ENGINES}${NC}"
+fi
 _cfg_row "TideSQL repo     : ${GREEN}${SCRIPT_DIR}${NC}"
 echo -e "${CYAN}╚$(printf '═%.0s' $(seq 1 68))╝${NC}"
 echo ""
@@ -442,6 +487,16 @@ build_mariadb() {
         -DWITH_UNIT_TESTS=OFF
     )
 
+    # Disable skipped engines
+    if [[ -n "$SKIP_ENGINES" ]]; then
+        IFS=',' read -ra _engines <<< "$SKIP_ENGINES"
+        for _eng in "${_engines[@]}"; do
+            _eng="$(echo "$_eng" | tr -d ' ' | tr '[:lower:]' '[:upper:]')"
+            cmake_args+=("-DPLUGIN_${_eng}=NO")
+            info "Skipping storage engine: ${_eng}"
+        done
+    fi
+
     case "$OS" in
         macos)
             local sdk_root cc cxx
@@ -722,6 +777,15 @@ pgo_instrument() {
 
     export TIDESDB_ROOT="${TIDESDB_PREFIX}"
 
+    # Disable skipped engines
+    if [[ -n "$SKIP_ENGINES" ]]; then
+        IFS=',' read -ra _engines <<< "$SKIP_ENGINES"
+        for _eng in "${_engines[@]}"; do
+            _eng="$(echo "$_eng" | tr -d ' ' | tr '[:lower:]' '[:upper:]')"
+            cmake_args+=("-DPLUGIN_${_eng}=NO")
+        done
+    fi
+
     case "$OS" in
         macos)
             local sdk_root cc cxx
@@ -805,6 +869,15 @@ pgo_optimize() {
 
     export TIDESDB_ROOT="${TIDESDB_PREFIX}"
 
+    # Disable skipped engines
+    if [[ -n "$SKIP_ENGINES" ]]; then
+        IFS=',' read -ra _engines <<< "$SKIP_ENGINES"
+        for _eng in "${_engines[@]}"; do
+            _eng="$(echo "$_eng" | tr -d ' ' | tr '[:lower:]' '[:upper:]')"
+            cmake_args+=("-DPLUGIN_${_eng}=NO")
+        done
+    fi
+
     case "$OS" in
         macos)
             local sdk_root cc cxx
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_alter_crash.result b/mysql-test/suite/tidesdb/r/tidesdb_alter_crash.result
new file mode 100644
index 0000000..f805363
--- /dev/null
+++ b/mysql-test/suite/tidesdb/r/tidesdb_alter_crash.result
@@ -0,0 +1,48 @@
+#
+# Issue #70: ALTER TABLE sometimes crashes MariaDB
+# The crash was caused by unbounded read-set growth during
+# ALTER TABLE's copy-phase scan under REPEATABLE_READ.
+#
+CREATE TABLE t_alt70 (
+a INT AUTO_INCREMENT PRIMARY KEY,
+b INT
+) ENGINE=TidesDB;
+INSERT INTO t_alt70 (a, b) VALUES (DEFAULT, 10), (DEFAULT, 20), (DEFAULT, 30);
+# Double the rows repeatedly to get ~100K rows
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+SELECT COUNT(*) FROM t_alt70;
+COUNT(*)
+98304
+# Switch to autocommit=0 so transactions use REPEATABLE_READ
+# (this is the scenario that triggered the crash)
+SET autocommit=0;
+# These ALTER TABLE statements reproduce the original bug sequence
+ALTER TABLE t_alt70 ADD PRIMARY KEY (a);
+ERROR 42000: Multiple primary key defined
+ALTER TABLE t_alt70 DROP PRIMARY KEY;
+ERROR 42000: Incorrect table definition; there can be only one auto column and it must be defined as a key
+# This copy-based ALTER TABLE scans ~100K rows; before the fix
+# it would crash in tidesdb_txn_add_to_read_set due to unbounded
+# read-set growth under REPEATABLE_READ.
+ALTER TABLE t_alt70 DROP PRIMARY KEY, CHANGE a a INT;
+SELECT COUNT(*) FROM t_alt70;
+COUNT(*)
+98304
+SET autocommit=1;
+DROP TABLE t_alt70;
+#
+# Done.
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_consistent_snapshot.result b/mysql-test/suite/tidesdb/r/tidesdb_consistent_snapshot.result
new file mode 100644
index 0000000..4a21c26
--- /dev/null
+++ b/mysql-test/suite/tidesdb/r/tidesdb_consistent_snapshot.result
@@ -0,0 +1,68 @@
+#
+# Issue #64: WITH CONSISTENT SNAPSHOT doesn't work
+#
+CREATE TABLE t_snap64 (
+a INT,
+b INT
+) ENGINE=TidesDB;
+# Seed some data so global_seq > 0
+INSERT INTO t_snap64 VALUES (100, 100);
+DELETE FROM t_snap64 WHERE a = 100;
+# ---- TEST 1: START TRANSACTION WITH CONSISTENT SNAPSHOT ----
+connect  con2, localhost, root,,;
+connection default;
+SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+# Insert from connection 2 AFTER snapshot
+connection con2;
+INSERT INTO t_snap64 (a, b) VALUES (1, 10);
+SELECT * FROM t_snap64 ORDER BY a;
+a	b
+1	10
+# Connection 1 should NOT see the row (snapshot was before insert)
+connection default;
+SELECT * FROM t_snap64 ORDER BY a;
+a	b
+COMMIT;
+# After COMMIT, a new snapshot should see the row
+SELECT * FROM t_snap64 ORDER BY a;
+a	b
+1	10
+# ---- TEST 2: Multiple inserts after snapshot ----
+SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+connection con2;
+INSERT INTO t_snap64 (a, b) VALUES (2, 20);
+INSERT INTO t_snap64 (a, b) VALUES (3, 30);
+connection default;
+# Should still only see row (1,10) from before the snapshot
+SELECT * FROM t_snap64 ORDER BY a;
+a	b
+1	10
+COMMIT;
+# After COMMIT, should see all 3 rows
+SELECT * FROM t_snap64 ORDER BY a;
+a	b
+1	10
+2	20
+3	30
+# ---- TEST 3: Without CONSISTENT SNAPSHOT, new data IS visible ----
+BEGIN;
+connection con2;
+INSERT INTO t_snap64 (a, b) VALUES (4, 40);
+connection default;
+# Without CONSISTENT SNAPSHOT, should see all 4 rows
+SELECT * FROM t_snap64 ORDER BY a;
+a	b
+1	10
+2	20
+3	30
+4	40
+COMMIT;
+# Cleanup
+connection con2;
+disconnect con2;
+connection default;
+DROP TABLE t_snap64;
+#
+# Done.
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_drop_create.result b/mysql-test/suite/tidesdb/r/tidesdb_drop_create.result
new file mode 100644
index 0000000..6ad9fbe
--- /dev/null
+++ b/mysql-test/suite/tidesdb/r/tidesdb_drop_create.result
@@ -0,0 +1,79 @@
+#
+# Issue #57: Data survives DROP + CREATE
+#
+# ---- TEST 1: DROP TABLE must destroy data ----
+CREATE TABLE t_drop57 (i INT NOT NULL PRIMARY KEY, v VARCHAR(50)) ENGINE=TidesDB;
+INSERT INTO t_drop57 VALUES (1, 'aaa'), (2, 'bbb'), (3, 'ccc');
+SELECT * FROM t_drop57 ORDER BY i;
+i	v
+1	aaa
+2	bbb
+3	ccc
+DROP TABLE t_drop57;
+CREATE TABLE t_drop57 (i INT NOT NULL PRIMARY KEY, v VARCHAR(50)) ENGINE=TidesDB;
+# Must be empty after DROP + CREATE
+SELECT COUNT(*) FROM t_drop57;
+COUNT(*)
+0
+SELECT * FROM t_drop57 ORDER BY i;
+i	v
+DROP TABLE t_drop57;
+# ---- TEST 2: CREATE OR REPLACE must destroy data ----
+CREATE TABLE t_cor57 (i INT) ENGINE=TidesDB;
+INSERT INTO t_cor57 VALUES (10), (20), (30);
+SELECT * FROM t_cor57 ORDER BY i;
+i
+10
+20
+30
+CREATE OR REPLACE TABLE t_cor57 (i INT) ENGINE=TidesDB;
+# Must be empty after CREATE OR REPLACE
+SELECT COUNT(*) FROM t_cor57;
+COUNT(*)
+0
+SELECT * FROM t_cor57 ORDER BY i;
+i
+DROP TABLE t_cor57;
+# ---- TEST 3: Secondary indexes must also be cleaned ----
+CREATE TABLE t_idx57 (
+id INT NOT NULL PRIMARY KEY,
+val INT NOT NULL,
+KEY idx_val (val)
+) ENGINE=TidesDB;
+INSERT INTO t_idx57 VALUES (1, 100), (2, 200), (3, 300);
+SELECT * FROM t_idx57 ORDER BY id;
+id	val
+1	100
+2	200
+3	300
+SELECT val FROM t_idx57 WHERE val = 200;
+val
+200
+DROP TABLE t_idx57;
+CREATE TABLE t_idx57 (
+id INT NOT NULL PRIMARY KEY,
+val INT NOT NULL,
+KEY idx_val (val)
+) ENGINE=TidesDB;
+# Must be empty after DROP + CREATE (including index)
+SELECT COUNT(*) FROM t_idx57;
+COUNT(*)
+0
+SELECT * FROM t_idx57 ORDER BY id;
+id	val
+SELECT val FROM t_idx57 WHERE val = 200;
+val
+DROP TABLE t_idx57;
+# ---- TEST 4: TRUNCATE TABLE still works ----
+CREATE TABLE t_trunc57 (i INT NOT NULL PRIMARY KEY) ENGINE=TidesDB;
+INSERT INTO t_trunc57 VALUES (1), (2), (3);
+SELECT COUNT(*) FROM t_trunc57;
+COUNT(*)
+3
+TRUNCATE TABLE t_trunc57;
+SELECT COUNT(*) FROM t_trunc57;
+COUNT(*)
+0
+DROP TABLE t_trunc57;
+#
+# Done.
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_fk_convert.result b/mysql-test/suite/tidesdb/r/tidesdb_fk_convert.result
new file mode 100644
index 0000000..baad469
--- /dev/null
+++ b/mysql-test/suite/tidesdb/r/tidesdb_fk_convert.result
@@ -0,0 +1,86 @@
+#
+# Issue #61: Converting InnoDB tables with foreign keys to TidesDB
+# Requires a server-side patch to sql/sql_table.cc that honours
+# FOREIGN_KEY_CHECKS=0 during can_switch_engines().  If the patch
+# is absent (upstream MariaDB), the test is skipped.
+#
+# Create an InnoDB table with a self-referencing foreign key
+CREATE TABLE t_fk61 (
+a INT,
+b INT NOT NULL,
+INDEX idx_a (a),
+CONSTRAINT `fk_self` FOREIGN KEY (b) REFERENCES t_fk61 (a)
+ON DELETE CASCADE
+ON UPDATE RESTRICT
+) ENGINE=InnoDB;
+INSERT INTO t_fk61 (a, b) VALUES (1, 1), (2, 1), (3, 2);
+SHOW CREATE TABLE t_fk61;
+Table	Create Table
+t_fk61	CREATE TABLE `t_fk61` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) NOT NULL,
+  KEY `idx_a` (`a`),
+  KEY `fk_self` (`b`),
+  CONSTRAINT `fk_self` FOREIGN KEY (`b`) REFERENCES `t_fk61` (`a`) ON DELETE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+# Without FOREIGN_KEY_CHECKS=0, the conversion should fail
+ALTER TABLE t_fk61 ENGINE=TidesDB;
+ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails
+# With FOREIGN_KEY_CHECKS=0, the conversion should succeed
+# (requires server patch; skip if absent)
+SET FOREIGN_KEY_CHECKS=0;
+ALTER TABLE t_fk61 ENGINE=TidesDB;
+SET FOREIGN_KEY_CHECKS=1;
+# Verify data survived the conversion
+SELECT * FROM t_fk61 ORDER BY a;
+a	b
+1	1
+2	1
+3	2
+# Verify the table is now TidesDB and FKs are gone
+SHOW CREATE TABLE t_fk61;
+Table	Create Table
+t_fk61	CREATE TABLE `t_fk61` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) NOT NULL,
+  KEY `idx_a` (`a`),
+  KEY `fk_self` (`b`)
+) ENGINE=TIDESDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+# Verify we can still do DML
+INSERT INTO t_fk61 (a, b) VALUES (4, 99);
+SELECT * FROM t_fk61 ORDER BY a;
+a	b
+1	1
+2	1
+3	2
+4	99
+DROP TABLE t_fk61;
+# Test with parent-child FK relationship (two tables)
+CREATE TABLE t_parent61 (
+id INT PRIMARY KEY
+) ENGINE=InnoDB;
+CREATE TABLE t_child61 (
+id INT PRIMARY KEY,
+parent_id INT,
+CONSTRAINT `fk_parent` FOREIGN KEY (parent_id) REFERENCES t_parent61 (id)
+) ENGINE=InnoDB;
+INSERT INTO t_parent61 VALUES (1), (2), (3);
+INSERT INTO t_child61 VALUES (10, 1), (20, 2);
+# Convert parent table with FK_CHECKS=0
+SET FOREIGN_KEY_CHECKS=0;
+ALTER TABLE t_parent61 ENGINE=TidesDB;
+ALTER TABLE t_child61 ENGINE=TidesDB;
+SET FOREIGN_KEY_CHECKS=1;
+SELECT * FROM t_parent61 ORDER BY id;
+id
+1
+2
+3
+SELECT * FROM t_child61 ORDER BY id;
+id	parent_id
+10	1
+20	2
+DROP TABLE t_child61;
+DROP TABLE t_parent61;
+#
+# Done.
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_info_schema.result b/mysql-test/suite/tidesdb/r/tidesdb_info_schema.result
new file mode 100644
index 0000000..ac88568
--- /dev/null
+++ b/mysql-test/suite/tidesdb/r/tidesdb_info_schema.result
@@ -0,0 +1,34 @@
+# ---- setup ----
+CREATE TABLE t_info_schema (
+id INT PRIMARY KEY,
+val VARCHAR(200)
+) ENGINE=TidesDB;
+INSERT INTO t_info_schema VALUES (1, REPEAT('a', 100));
+INSERT INTO t_info_schema VALUES (2, REPEAT('b', 100));
+INSERT INTO t_info_schema VALUES (3, REPEAT('c', 100));
+# ---- data_length must be non-zero ----
+OK: DATA_LENGTH > 0
+# ---- table_rows must reflect inserted rows ----
+OK: TABLE_ROWS >= 3
+# ---- add secondary index and check index_length ----
+ALTER TABLE t_info_schema ADD INDEX idx_val (val);
+Warnings:
+Note	1071	Specified key was too long; max key length is 255 bytes
+SELECT COUNT(*) FROM t_info_schema;
+COUNT(*)
+3
+OK: INDEX_LENGTH > 0
+# ---- verify after bulk insert ----
+SELECT COUNT(*) FROM t_info_schema;
+COUNT(*)
+200
+OK: DATA_LENGTH > 0 after bulk insert
+# ---- create_time must be non-null ----
+OK: CREATE_TIME is set
+# ---- update_time must be non-null after DML ----
+OK: UPDATE_TIME is set
+# ---- update_time advances after more DML ----
+INSERT INTO t_info_schema VALUES (9999, 'timestamp_test');
+OK: UPDATE_TIME advanced after INSERT
+# ---- cleanup ----
+DROP TABLE t_info_schema;
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_online_ddl.result b/mysql-test/suite/tidesdb/r/tidesdb_online_ddl.result
index 27f6708..2f1ad8b 100644
--- a/mysql-test/suite/tidesdb/r/tidesdb_online_ddl.result
+++ b/mysql-test/suite/tidesdb/r/tidesdb_online_ddl.result
@@ -1,31 +1,31 @@
 # ---- Setup ----
-CREATE TABLE t1 (
+CREATE TABLE t_ddl (
 id INT PRIMARY KEY,
 a INT,
 b VARCHAR(100),
 c INT DEFAULT 0
 ) ENGINE=TidesDB;
-INSERT INTO t1 VALUES (1, 10, 'alpha', 100);
-INSERT INTO t1 VALUES (2, 20, 'beta', 200);
-INSERT INTO t1 VALUES (3, 30, 'gamma', 300);
-INSERT INTO t1 VALUES (4, 10, 'delta', 400);
-INSERT INTO t1 VALUES (5, 50, 'epsilon', 500);
+INSERT INTO t_ddl VALUES (1, 10, 'alpha', 100);
+INSERT INTO t_ddl VALUES (2, 20, 'beta', 200);
+INSERT INTO t_ddl VALUES (3, 30, 'gamma', 300);
+INSERT INTO t_ddl VALUES (4, 10, 'delta', 400);
+INSERT INTO t_ddl VALUES (5, 50, 'epsilon', 500);
 # ---- INSTANT: change column default ----
-ALTER TABLE t1 ALTER COLUMN c SET DEFAULT 999, ALGORITHM=INSTANT;
-INSERT INTO t1 (id, a, b) VALUES (6, 60, 'zeta');
-SELECT id, c FROM t1 WHERE id = 6;
+ALTER TABLE t_ddl ALTER COLUMN c SET DEFAULT 999, ALGORITHM=INSTANT;
+INSERT INTO t_ddl (id, a, b) VALUES (6, 60, 'zeta');
+SELECT id, c FROM t_ddl WHERE id = 6;
 id	c
 6	999
 # ---- INSTANT: rename column ----
-ALTER TABLE t1 CHANGE b b_name VARCHAR(100), ALGORITHM=INSTANT;
-SELECT id, b_name FROM t1 WHERE id = 1;
+ALTER TABLE t_ddl CHANGE b b_name VARCHAR(100), ALGORITHM=INSTANT;
+SELECT id, b_name FROM t_ddl WHERE id = 1;
 id	b_name
 1	alpha
 # ---- INSTANT: change table option (SYNC_MODE) ----
-ALTER TABLE t1 SYNC_MODE='NONE', ALGORITHM=INSTANT;
-SHOW CREATE TABLE t1;
+ALTER TABLE t_ddl SYNC_MODE='NONE', ALGORITHM=INSTANT;
+SHOW CREATE TABLE t_ddl;
 Table	Create Table
-t1	CREATE TABLE `t1` (
+t_ddl	CREATE TABLE `t_ddl` (
   `id` int(11) NOT NULL,
   `a` int(11) DEFAULT NULL,
   `b_name` varchar(100) DEFAULT NULL,
@@ -33,71 +33,71 @@ t1	CREATE TABLE `t1` (
   PRIMARY KEY (`id`)
 ) ENGINE=TIDESDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci `SYNC_MODE`='NONE'
 # ---- INPLACE: add secondary index ----
-ALTER TABLE t1 ADD INDEX idx_a (a), ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
+ALTER TABLE t_ddl ADD INDEX idx_a (a), ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
-t1	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
-t1	1	idx_a	1	a	A	6	NULL	NULL	YES	BTREE			NO
+t_ddl	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
+t_ddl	1	idx_a	1	a	A	6	NULL	NULL	YES	BTREE			NO
 # Verify index is usable
-SELECT id, a FROM t1 WHERE a = 10 ORDER BY id;
+SELECT id, a FROM t_ddl WHERE a = 10 ORDER BY id;
 id	a
 1	10
 4	10
-SELECT id, a FROM t1 WHERE a >= 30 ORDER BY a;
+SELECT id, a FROM t_ddl WHERE a >= 30 ORDER BY a;
 id	a
 3	30
 5	50
 6	60
 # ---- INPLACE: add another index ----
-ALTER TABLE t1 ADD INDEX idx_c (c), ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
+ALTER TABLE t_ddl ADD INDEX idx_c (c), ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
-t1	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
-t1	1	idx_a	1	a	A	6	NULL	NULL	YES	BTREE			NO
-t1	1	idx_c	1	c	A	6	NULL	NULL	YES	BTREE			NO
-EXPLAIN SELECT id, c FROM t1 WHERE c = 200;
+t_ddl	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
+t_ddl	1	idx_a	1	a	A	6	NULL	NULL	YES	BTREE			NO
+t_ddl	1	idx_c	1	c	A	6	NULL	NULL	YES	BTREE			NO
+EXPLAIN SELECT id, c FROM t_ddl WHERE c = 200;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	idx_c	idx_c	5	const	1	Using index
-SELECT id, c FROM t1 WHERE c = 200;
+1	SIMPLE	t_ddl	ref	idx_c	idx_c	5	const	1	Using index
+SELECT id, c FROM t_ddl WHERE c = 200;
 id	c
 2	200
 # ---- INPLACE: drop index ----
-ALTER TABLE t1 DROP INDEX idx_a, ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
+ALTER TABLE t_ddl DROP INDEX idx_a, ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
-t1	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
-t1	1	idx_c	1	c	A	6	NULL	NULL	YES	BTREE			NO
+t_ddl	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
+t_ddl	1	idx_c	1	c	A	6	NULL	NULL	YES	BTREE			NO
 # Verify remaining index still works
-SELECT id, c FROM t1 WHERE c = 300;
+SELECT id, c FROM t_ddl WHERE c = 300;
 id	c
 3	300
 # ---- INPLACE: add + drop in one statement ----
-ALTER TABLE t1 ADD INDEX idx_a2 (a), DROP INDEX idx_c, ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
+ALTER TABLE t_ddl ADD INDEX idx_a2 (a), DROP INDEX idx_c, ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
-t1	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
-t1	1	idx_a2	1	a	A	6	NULL	NULL	YES	BTREE			NO
-EXPLAIN SELECT id, a FROM t1 WHERE a = 20;
+t_ddl	0	PRIMARY	1	id	A	6	NULL	NULL		BTREE			NO
+t_ddl	1	idx_a2	1	a	A	6	NULL	NULL	YES	BTREE			NO
+EXPLAIN SELECT id, a FROM t_ddl WHERE a = 20;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	idx_a2	idx_a2	5	const	1	Using index
-SELECT id, a FROM t1 WHERE a = 20;
+1	SIMPLE	t_ddl	ref	idx_a2	idx_a2	5	const	1	Using index
+SELECT id, a FROM t_ddl WHERE a = 20;
 id	a
 2	20
 # ---- COPY fallback: add column ----
-ALTER TABLE t1 ADD COLUMN d INT DEFAULT 0;
-SELECT id, d FROM t1 WHERE id = 1;
+ALTER TABLE t_ddl ADD COLUMN d INT DEFAULT 0;
+SELECT id, d FROM t_ddl WHERE id = 1;
 id	d
 1	0
 # ---- COPY fallback: drop column ----
-ALTER TABLE t1 DROP COLUMN d;
-SELECT * FROM t1 WHERE id = 1;
+ALTER TABLE t_ddl DROP COLUMN d;
+SELECT * FROM t_ddl WHERE id = 1;
 id	a	b_name	c
 1	10	alpha	100
 # ---- Verify ALGORITHM=INPLACE rejected for column changes ----
-ALTER TABLE t1 ADD COLUMN e INT, ALGORITHM=INPLACE;
+ALTER TABLE t_ddl ADD COLUMN e INT, ALGORITHM=INPLACE;
 ERROR 0A000: ALGORITHM=INPLACE is not supported for this operation. Try ALGORITHM=COPY
 # ---- Cleanup ----
-DROP TABLE t1;
+DROP TABLE t_ddl;
 # ---- Test with data and hidden PK (no explicit PK) ----
 CREATE TABLE t_nopk (
 a INT,
@@ -114,3 +114,24 @@ a	b
 # Drop it
 ALTER TABLE t_nopk DROP INDEX idx_a, ALGORITHM=INPLACE;
 DROP TABLE t_nopk;
+# ---- ADD UNIQUE must reject duplicates ----
+CREATE TABLE t_dup (
+i INT NOT NULL,
+j INT NOT NULL DEFAULT 0
+) ENGINE=TidesDB;
+INSERT INTO t_dup VALUES (1, 0);
+INSERT INTO t_dup VALUES (2, 0);
+SELECT * FROM t_dup ORDER BY i;
+i	j
+1	0
+2	0
+ALTER TABLE t_dup ADD UNIQUE unq_j (j);
+ERROR 23000: Duplicate entry '0' for key 'unq_j'
+SELECT * FROM t_dup ORDER BY i;
+i	j
+1	0
+2	0
+SELECT COUNT(*) FROM t_dup;
+COUNT(*)
+2
+DROP TABLE t_dup;
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_stress.result b/mysql-test/suite/tidesdb/r/tidesdb_stress.result
index b2adc02..72a9363 100644
--- a/mysql-test/suite/tidesdb/r/tidesdb_stress.result
+++ b/mysql-test/suite/tidesdb/r/tidesdb_stress.result
@@ -449,17 +449,19 @@ min_s	max_s
 COMMIT;
 #
 # ============================================
-# TEST 19: Duplicate PK insert in transaction (upsert semantics)
-#   TidesDB uses KV put-overwrites, so a duplicate PK INSERT
-#   acts as an upsert.  Verify the txn continues and the
-#   last write wins.
+# TEST 19: PK uniqueness enforcement and REPLACE INTO
+#   Duplicate PK INSERT must return an error.
+#   REPLACE INTO overwrites the existing row.
 # ============================================
 #
 CREATE TABLE stress_uniq (id INT PRIMARY KEY, val VARCHAR(50)) ENGINE=TIDESDB;
 INSERT INTO stress_uniq VALUES (1, 'first');
+INSERT INTO stress_uniq VALUES (1, 'should_fail');
+ERROR 23000: Duplicate entry '1' for key 'PRIMARY'
+REPLACE INTO stress_uniq VALUES (1, 'replaced');
 BEGIN;
 INSERT INTO stress_uniq VALUES (2, 'second');
-INSERT INTO stress_uniq VALUES (1, 'overwritten');
+REPLACE INTO stress_uniq VALUES (1, 'overwritten');
 INSERT INTO stress_uniq VALUES (3, 'third');
 COMMIT;
 SELECT * FROM stress_uniq ORDER BY id;
diff --git a/mysql-test/suite/tidesdb/r/tidesdb_ttl.result b/mysql-test/suite/tidesdb/r/tidesdb_ttl.result
index b891ce4..dab0936 100644
--- a/mysql-test/suite/tidesdb/r/tidesdb_ttl.result
+++ b/mysql-test/suite/tidesdb/r/tidesdb_ttl.result
@@ -121,5 +121,79 @@ t_ttl_show	CREATE TABLE `t_ttl_show` (
 ) ENGINE=TIDESDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci `TTL`=3600
 DROP TABLE t_ttl_show;
 #
+# ============================================
+# TEST 7: Session TTL override (SET SESSION)
+#   Table has no TTL; session variable applies
+# ============================================
+#
+CREATE TABLE t_ttl_sess (
+id INT PRIMARY KEY,
+val VARCHAR(50)
+) ENGINE=TIDESDB;
+# Default session TTL is 0 (no override)
+SELECT @@session.tidesdb_ttl;
+@@session.tidesdb_ttl
+0
+SET SESSION tidesdb_ttl = 2;
+INSERT INTO t_ttl_sess VALUES (1, 'session_ttl'), (2, 'also_session');
+# Rows visible immediately
+SELECT * FROM t_ttl_sess ORDER BY id;
+id	val
+1	session_ttl
+2	also_session
+SET SESSION tidesdb_ttl = 0;
+# Wait for session TTL to expire (3s > 2s)
+# Rows should now be expired
+SELECT * FROM t_ttl_sess ORDER BY id;
+id	val
+DROP TABLE t_ttl_sess;
+#
+# ============================================
+# TEST 8: SET STATEMENT tidesdb_ttl=N FOR ...
+#   Only the single statement gets TTL
+# ============================================
+#
+CREATE TABLE t_ttl_stmt (
+id INT PRIMARY KEY,
+val VARCHAR(50)
+) ENGINE=TIDESDB;
+SET STATEMENT tidesdb_ttl=2 FOR
+INSERT INTO t_ttl_stmt VALUES (1, 'short_lived');
+INSERT INTO t_ttl_stmt VALUES (2, 'permanent');
+# Both rows visible immediately
+SELECT * FROM t_ttl_stmt ORDER BY id;
+id	val
+1	short_lived
+2	permanent
+# Row 1 expired (session TTL=2); row 2 still alive (no TTL)
+SELECT * FROM t_ttl_stmt ORDER BY id;
+id	val
+2	permanent
+DROP TABLE t_ttl_stmt;
+#
+# ============================================
+# TEST 9: Session TTL does NOT override per-row TTL_COL
+# ============================================
+#
+CREATE TABLE t_ttl_priority (
+id INT PRIMARY KEY,
+val VARCHAR(50),
+row_ttl INT `TTL`=1
+) ENGINE=TIDESDB;
+SET SESSION tidesdb_ttl = 86400;
+INSERT INTO t_ttl_priority VALUES (1, 'per_row_wins', 2);
+INSERT INTO t_ttl_priority VALUES (2, 'uses_session', 0);
+SET SESSION tidesdb_ttl = 0;
+# Both visible immediately
+SELECT id, val FROM t_ttl_priority ORDER BY id;
+id	val
+1	per_row_wins
+2	uses_session
+# Row 1 expired (per-row TTL=2 wins); row 2 still alive (session TTL=86400)
+SELECT id, val FROM t_ttl_priority ORDER BY id;
+id	val
+2	uses_session
+DROP TABLE t_ttl_priority;
+#
 #
 # Done.
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_alter_crash.opt b/mysql-test/suite/tidesdb/t/tidesdb_alter_crash.opt
new file mode 100644
index 0000000..2f9ea4e
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_alter_crash.opt
@@ -0,0 +1,2 @@
+--plugin-maturity=unknown
+--plugin-load-add=ha_tidesdb
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_alter_crash.test b/mysql-test/suite/tidesdb/t/tidesdb_alter_crash.test
new file mode 100644
index 0000000..e5a67af
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_alter_crash.test
@@ -0,0 +1,46 @@
+--echo #
+--echo # Issue #70: ALTER TABLE sometimes crashes MariaDB
+--echo # The crash was caused by unbounded read-set growth during
+--echo # ALTER TABLE's copy-phase scan under REPEATABLE_READ.
+--echo #
+
+CREATE TABLE t_alt70 (
+    a INT AUTO_INCREMENT PRIMARY KEY,
+    b INT
+) ENGINE=TidesDB;
+
+INSERT INTO t_alt70 (a, b) VALUES (DEFAULT, 10), (DEFAULT, 20), (DEFAULT, 30);
+
+--echo # Double the rows repeatedly to get ~100K rows
+let $i = 15;
+while ($i)
+{
+  INSERT INTO t_alt70 (b) SELECT b FROM t_alt70;
+  dec $i;
+}
+
+SELECT COUNT(*) FROM t_alt70;
+
+--echo # Switch to autocommit=0 so transactions use REPEATABLE_READ
+--echo # (this is the scenario that triggered the crash)
+SET autocommit=0;
+
+--echo # These ALTER TABLE statements reproduce the original bug sequence
+--error ER_MULTIPLE_PRI_KEY
+ALTER TABLE t_alt70 ADD PRIMARY KEY (a);
+
+--error ER_WRONG_AUTO_KEY
+ALTER TABLE t_alt70 DROP PRIMARY KEY;
+
+--echo # This copy-based ALTER TABLE scans ~100K rows; before the fix
+--echo # it would crash in tidesdb_txn_add_to_read_set due to unbounded
+--echo # read-set growth under REPEATABLE_READ.
+ALTER TABLE t_alt70 DROP PRIMARY KEY, CHANGE a a INT;
+
+SELECT COUNT(*) FROM t_alt70;
+
+SET autocommit=1;
+DROP TABLE t_alt70;
+
+--echo #
+--echo # Done.
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_consistent_snapshot.opt b/mysql-test/suite/tidesdb/t/tidesdb_consistent_snapshot.opt
new file mode 100644
index 0000000..2f9ea4e
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_consistent_snapshot.opt
@@ -0,0 +1,2 @@
+--plugin-maturity=unknown
+--plugin-load-add=ha_tidesdb
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_consistent_snapshot.test b/mysql-test/suite/tidesdb/t/tidesdb_consistent_snapshot.test
new file mode 100644
index 0000000..7b6b965
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_consistent_snapshot.test
@@ -0,0 +1,75 @@
+--echo #
+--echo # Issue #64: WITH CONSISTENT SNAPSHOT doesn't work
+--echo #
+
+CREATE TABLE t_snap64 (
+  a INT,
+  b INT
+) ENGINE=TidesDB;
+
+--echo # Seed some data so global_seq > 0
+INSERT INTO t_snap64 VALUES (100, 100);
+DELETE FROM t_snap64 WHERE a = 100;
+
+--echo # ---- TEST 1: START TRANSACTION WITH CONSISTENT SNAPSHOT ----
+
+connect (con2, localhost, root,,);
+connection default;
+
+SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+
+--echo # Insert from connection 2 AFTER snapshot
+connection con2;
+INSERT INTO t_snap64 (a, b) VALUES (1, 10);
+SELECT * FROM t_snap64 ORDER BY a;
+
+--echo # Connection 1 should NOT see the row (snapshot was before insert)
+connection default;
+SELECT * FROM t_snap64 ORDER BY a;
+
+COMMIT;
+
+--echo # After COMMIT, a new snapshot should see the row
+SELECT * FROM t_snap64 ORDER BY a;
+
+--echo # ---- TEST 2: Multiple inserts after snapshot ----
+
+SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+
+connection con2;
+INSERT INTO t_snap64 (a, b) VALUES (2, 20);
+INSERT INTO t_snap64 (a, b) VALUES (3, 30);
+
+connection default;
+--echo # Should still only see row (1,10) from before the snapshot
+SELECT * FROM t_snap64 ORDER BY a;
+
+COMMIT;
+
+--echo # After COMMIT, should see all 3 rows
+SELECT * FROM t_snap64 ORDER BY a;
+
+--echo # ---- TEST 3: Without CONSISTENT SNAPSHOT, new data IS visible ----
+
+BEGIN;
+
+connection con2;
+INSERT INTO t_snap64 (a, b) VALUES (4, 40);
+
+connection default;
+--echo # Without CONSISTENT SNAPSHOT, should see all 4 rows
+SELECT * FROM t_snap64 ORDER BY a;
+
+COMMIT;
+
+--echo # Cleanup
+connection con2;
+disconnect con2;
+connection default;
+
+DROP TABLE t_snap64;
+
+--echo #
+--echo # Done.
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_drop_create.opt b/mysql-test/suite/tidesdb/t/tidesdb_drop_create.opt
new file mode 100644
index 0000000..2f9ea4e
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_drop_create.opt
@@ -0,0 +1,2 @@
+--plugin-maturity=unknown
+--plugin-load-add=ha_tidesdb
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_drop_create.test b/mysql-test/suite/tidesdb/t/tidesdb_drop_create.test
new file mode 100644
index 0000000..ccfbd4b
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_drop_create.test
@@ -0,0 +1,74 @@
+--echo #
+--echo # Issue #57: Data survives DROP + CREATE
+--echo #
+
+--echo # ---- TEST 1: DROP TABLE must destroy data ----
+CREATE TABLE t_drop57 (i INT NOT NULL PRIMARY KEY, v VARCHAR(50)) ENGINE=TidesDB;
+
+INSERT INTO t_drop57 VALUES (1, 'aaa'), (2, 'bbb'), (3, 'ccc');
+SELECT * FROM t_drop57 ORDER BY i;
+
+DROP TABLE t_drop57;
+
+CREATE TABLE t_drop57 (i INT NOT NULL PRIMARY KEY, v VARCHAR(50)) ENGINE=TidesDB;
+
+--echo # Must be empty after DROP + CREATE
+SELECT COUNT(*) FROM t_drop57;
+SELECT * FROM t_drop57 ORDER BY i;
+
+DROP TABLE t_drop57;
+
+--echo # ---- TEST 2: CREATE OR REPLACE must destroy data ----
+CREATE TABLE t_cor57 (i INT) ENGINE=TidesDB;
+
+INSERT INTO t_cor57 VALUES (10), (20), (30);
+SELECT * FROM t_cor57 ORDER BY i;
+
+CREATE OR REPLACE TABLE t_cor57 (i INT) ENGINE=TidesDB;
+
+--echo # Must be empty after CREATE OR REPLACE
+SELECT COUNT(*) FROM t_cor57;
+SELECT * FROM t_cor57 ORDER BY i;
+
+DROP TABLE t_cor57;
+
+--echo # ---- TEST 3: Secondary indexes must also be cleaned ----
+CREATE TABLE t_idx57 (
+  id INT NOT NULL PRIMARY KEY,
+  val INT NOT NULL,
+  KEY idx_val (val)
+) ENGINE=TidesDB;
+
+INSERT INTO t_idx57 VALUES (1, 100), (2, 200), (3, 300);
+SELECT * FROM t_idx57 ORDER BY id;
+SELECT val FROM t_idx57 WHERE val = 200;
+
+DROP TABLE t_idx57;
+
+CREATE TABLE t_idx57 (
+  id INT NOT NULL PRIMARY KEY,
+  val INT NOT NULL,
+  KEY idx_val (val)
+) ENGINE=TidesDB;
+
+--echo # Must be empty after DROP + CREATE (including index)
+SELECT COUNT(*) FROM t_idx57;
+SELECT * FROM t_idx57 ORDER BY id;
+SELECT val FROM t_idx57 WHERE val = 200;
+
+DROP TABLE t_idx57;
+
+--echo # ---- TEST 4: TRUNCATE TABLE still works ----
+CREATE TABLE t_trunc57 (i INT NOT NULL PRIMARY KEY) ENGINE=TidesDB;
+
+INSERT INTO t_trunc57 VALUES (1), (2), (3);
+SELECT COUNT(*) FROM t_trunc57;
+
+TRUNCATE TABLE t_trunc57;
+
+SELECT COUNT(*) FROM t_trunc57;
+
+DROP TABLE t_trunc57;
+
+--echo #
+--echo # Done.
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_fk_convert.opt b/mysql-test/suite/tidesdb/t/tidesdb_fk_convert.opt
new file mode 100644
index 0000000..2f9ea4e
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_fk_convert.opt
@@ -0,0 +1,2 @@
+--plugin-maturity=unknown
+--plugin-load-add=ha_tidesdb
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_fk_convert.test b/mysql-test/suite/tidesdb/t/tidesdb_fk_convert.test
new file mode 100644
index 0000000..a16e6a1
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_fk_convert.test
@@ -0,0 +1,81 @@
+--echo #
+--echo # Issue #61: Converting InnoDB tables with foreign keys to TidesDB
+--echo # Requires a server-side patch to sql/sql_table.cc that honours
+--echo # FOREIGN_KEY_CHECKS=0 during can_switch_engines().  If the patch
+--echo # is absent (upstream MariaDB), the test is skipped.
+--echo #
+
+--source include/have_innodb.inc
+
+--echo # Create an InnoDB table with a self-referencing foreign key
+CREATE TABLE t_fk61 (
+  a INT,
+  b INT NOT NULL,
+  INDEX idx_a (a),
+  CONSTRAINT `fk_self` FOREIGN KEY (b) REFERENCES t_fk61 (a)
+    ON DELETE CASCADE
+    ON UPDATE RESTRICT
+) ENGINE=InnoDB;
+
+INSERT INTO t_fk61 (a, b) VALUES (1, 1), (2, 1), (3, 2);
+
+SHOW CREATE TABLE t_fk61;
+
+--echo # Without FOREIGN_KEY_CHECKS=0, the conversion should fail
+--error ER_ROW_IS_REFERENCED
+ALTER TABLE t_fk61 ENGINE=TidesDB;
+
+--echo # With FOREIGN_KEY_CHECKS=0, the conversion should succeed
+--echo # (requires server patch; skip if absent)
+SET FOREIGN_KEY_CHECKS=0;
+--error 0,ER_ROW_IS_REFERENCED
+ALTER TABLE t_fk61 ENGINE=TidesDB;
+SET FOREIGN_KEY_CHECKS=1;
+
+if (`SELECT ENGINE != 'TidesDB' FROM information_schema.TABLES WHERE TABLE_NAME='t_fk61'`)
+{
+  --echo # Server does not have the sql/sql_table.cc FK patch -- skipping rest of test
+  DROP TABLE t_fk61;
+  --skip Server lacks sql/sql_table.cc FK conversion patch (issue #61)
+}
+
+--echo # Verify data survived the conversion
+SELECT * FROM t_fk61 ORDER BY a;
+
+--echo # Verify the table is now TidesDB and FKs are gone
+SHOW CREATE TABLE t_fk61;
+
+--echo # Verify we can still do DML
+INSERT INTO t_fk61 (a, b) VALUES (4, 99);
+SELECT * FROM t_fk61 ORDER BY a;
+
+DROP TABLE t_fk61;
+
+--echo # Test with parent-child FK relationship (two tables)
+CREATE TABLE t_parent61 (
+  id INT PRIMARY KEY
+) ENGINE=InnoDB;
+
+CREATE TABLE t_child61 (
+  id INT PRIMARY KEY,
+  parent_id INT,
+  CONSTRAINT `fk_parent` FOREIGN KEY (parent_id) REFERENCES t_parent61 (id)
+) ENGINE=InnoDB;
+
+INSERT INTO t_parent61 VALUES (1), (2), (3);
+INSERT INTO t_child61 VALUES (10, 1), (20, 2);
+
+--echo # Convert parent table with FK_CHECKS=0
+SET FOREIGN_KEY_CHECKS=0;
+ALTER TABLE t_parent61 ENGINE=TidesDB;
+ALTER TABLE t_child61 ENGINE=TidesDB;
+SET FOREIGN_KEY_CHECKS=1;
+
+SELECT * FROM t_parent61 ORDER BY id;
+SELECT * FROM t_child61 ORDER BY id;
+
+DROP TABLE t_child61;
+DROP TABLE t_parent61;
+
+--echo #
+--echo # Done.
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_info_schema.opt b/mysql-test/suite/tidesdb/t/tidesdb_info_schema.opt
new file mode 100644
index 0000000..8374626
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_info_schema.opt
@@ -0,0 +1 @@
+--plugin-maturity=unknown
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_info_schema.test b/mysql-test/suite/tidesdb/t/tidesdb_info_schema.test
new file mode 100644
index 0000000..fab15bd
--- /dev/null
+++ b/mysql-test/suite/tidesdb/t/tidesdb_info_schema.test
@@ -0,0 +1,125 @@
+#
+# TidesDB information_schema.TABLES size reporting
+# Verify DATA_LENGTH and INDEX_LENGTH are non-zero after inserts
+#
+
+--echo # ---- setup ----
+CREATE TABLE t_info_schema (
+  id INT PRIMARY KEY,
+  val VARCHAR(200)
+) ENGINE=TidesDB;
+
+INSERT INTO t_info_schema VALUES (1, REPEAT('a', 100));
+INSERT INTO t_info_schema VALUES (2, REPEAT('b', 100));
+INSERT INTO t_info_schema VALUES (3, REPEAT('c', 100));
+
+--echo # ---- data_length must be non-zero ----
+let $data_len = `SELECT DATA_LENGTH FROM information_schema.TABLES
+                  WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+if (!$data_len)
+{
+  --echo FAIL: DATA_LENGTH is 0
+}
+if ($data_len)
+{
+  --echo OK: DATA_LENGTH > 0
+}
+
+--echo # ---- table_rows must reflect inserted rows ----
+let $rows = `SELECT TABLE_ROWS FROM information_schema.TABLES
+              WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+if ($rows < 3)
+{
+  --echo FAIL: TABLE_ROWS < 3
+}
+if ($rows >= 3)
+{
+  --echo OK: TABLE_ROWS >= 3
+}
+
+--echo # ---- add secondary index and check index_length ----
+ALTER TABLE t_info_schema ADD INDEX idx_val (val);
+
+# force stats refresh (2s cache)
+--sleep 3
+
+# touch the table so info() is called fresh
+SELECT COUNT(*) FROM t_info_schema;
+
+let $idx_len = `SELECT INDEX_LENGTH FROM information_schema.TABLES
+                 WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+if (!$idx_len)
+{
+  --echo FAIL: INDEX_LENGTH is 0
+}
+if ($idx_len)
+{
+  --echo OK: INDEX_LENGTH > 0
+}
+
+--echo # ---- verify after bulk insert ----
+--disable_query_log
+let $i = 4;
+while ($i <= 200)
+{
+  eval INSERT INTO t_info_schema VALUES ($i, REPEAT('x', 100));
+  inc $i;
+}
+--enable_query_log
+
+--sleep 3
+SELECT COUNT(*) FROM t_info_schema;
+
+let $data_len2 = `SELECT DATA_LENGTH FROM information_schema.TABLES
+                   WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+if (!$data_len2)
+{
+  --echo FAIL: DATA_LENGTH is 0 after bulk insert
+}
+if ($data_len2)
+{
+  --echo OK: DATA_LENGTH > 0 after bulk insert
+}
+
+--echo # ---- create_time must be non-null ----
+let $ct = `SELECT CREATE_TIME FROM information_schema.TABLES
+            WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+if (!$ct)
+{
+  --echo FAIL: CREATE_TIME is NULL
+}
+if ($ct)
+{
+  --echo OK: CREATE_TIME is set
+}
+
+--echo # ---- update_time must be non-null after DML ----
+let $ut = `SELECT UPDATE_TIME FROM information_schema.TABLES
+            WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+if (!$ut)
+{
+  --echo FAIL: UPDATE_TIME is NULL
+}
+if ($ut)
+{
+  --echo OK: UPDATE_TIME is set
+}
+
+--echo # ---- update_time advances after more DML ----
+let $ut1 = `SELECT UNIX_TIMESTAMP(UPDATE_TIME) FROM information_schema.TABLES
+             WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+--sleep 2
+INSERT INTO t_info_schema VALUES (9999, 'timestamp_test');
+let $ut2 = `SELECT UNIX_TIMESTAMP(UPDATE_TIME) FROM information_schema.TABLES
+             WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 't_info_schema'`;
+if ($ut2 >= $ut1)
+{
+  --echo OK: UPDATE_TIME advanced after INSERT
+}
+if ($ut2 < $ut1)
+{
+  --echo FAIL: UPDATE_TIME did not advance
+}
+
+--echo # ---- cleanup ----
+DROP TABLE t_info_schema;
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_online_ddl.test b/mysql-test/suite/tidesdb/t/tidesdb_online_ddl.test
index e136d19..2c12d96 100644
--- a/mysql-test/suite/tidesdb/t/tidesdb_online_ddl.test
+++ b/mysql-test/suite/tidesdb/t/tidesdb_online_ddl.test
@@ -4,73 +4,73 @@
 #
 
 --echo # ---- Setup ----
-CREATE TABLE t1 (
+CREATE TABLE t_ddl (
   id INT PRIMARY KEY,
   a INT,
   b VARCHAR(100),
   c INT DEFAULT 0
 ) ENGINE=TidesDB;
 
-INSERT INTO t1 VALUES (1, 10, 'alpha', 100);
-INSERT INTO t1 VALUES (2, 20, 'beta', 200);
-INSERT INTO t1 VALUES (3, 30, 'gamma', 300);
-INSERT INTO t1 VALUES (4, 10, 'delta', 400);
-INSERT INTO t1 VALUES (5, 50, 'epsilon', 500);
+INSERT INTO t_ddl VALUES (1, 10, 'alpha', 100);
+INSERT INTO t_ddl VALUES (2, 20, 'beta', 200);
+INSERT INTO t_ddl VALUES (3, 30, 'gamma', 300);
+INSERT INTO t_ddl VALUES (4, 10, 'delta', 400);
+INSERT INTO t_ddl VALUES (5, 50, 'epsilon', 500);
 
 --echo # ---- INSTANT: change column default ----
-ALTER TABLE t1 ALTER COLUMN c SET DEFAULT 999, ALGORITHM=INSTANT;
-INSERT INTO t1 (id, a, b) VALUES (6, 60, 'zeta');
-SELECT id, c FROM t1 WHERE id = 6;
+ALTER TABLE t_ddl ALTER COLUMN c SET DEFAULT 999, ALGORITHM=INSTANT;
+INSERT INTO t_ddl (id, a, b) VALUES (6, 60, 'zeta');
+SELECT id, c FROM t_ddl WHERE id = 6;
 
 --echo # ---- INSTANT: rename column ----
-ALTER TABLE t1 CHANGE b b_name VARCHAR(100), ALGORITHM=INSTANT;
-SELECT id, b_name FROM t1 WHERE id = 1;
+ALTER TABLE t_ddl CHANGE b b_name VARCHAR(100), ALGORITHM=INSTANT;
+SELECT id, b_name FROM t_ddl WHERE id = 1;
 
 --echo # ---- INSTANT: change table option (SYNC_MODE) ----
-ALTER TABLE t1 SYNC_MODE='NONE', ALGORITHM=INSTANT;
-SHOW CREATE TABLE t1;
+ALTER TABLE t_ddl SYNC_MODE='NONE', ALGORITHM=INSTANT;
+SHOW CREATE TABLE t_ddl;
 
 --echo # ---- INPLACE: add secondary index ----
-ALTER TABLE t1 ADD INDEX idx_a (a), ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
+ALTER TABLE t_ddl ADD INDEX idx_a (a), ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
 
 --echo # Verify index is usable
-SELECT id, a FROM t1 WHERE a = 10 ORDER BY id;
-SELECT id, a FROM t1 WHERE a >= 30 ORDER BY a;
+SELECT id, a FROM t_ddl WHERE a = 10 ORDER BY id;
+SELECT id, a FROM t_ddl WHERE a >= 30 ORDER BY a;
 
 --echo # ---- INPLACE: add another index ----
-ALTER TABLE t1 ADD INDEX idx_c (c), ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
-EXPLAIN SELECT id, c FROM t1 WHERE c = 200;
-SELECT id, c FROM t1 WHERE c = 200;
+ALTER TABLE t_ddl ADD INDEX idx_c (c), ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
+EXPLAIN SELECT id, c FROM t_ddl WHERE c = 200;
+SELECT id, c FROM t_ddl WHERE c = 200;
 
 --echo # ---- INPLACE: drop index ----
-ALTER TABLE t1 DROP INDEX idx_a, ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
+ALTER TABLE t_ddl DROP INDEX idx_a, ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
 
 --echo # Verify remaining index still works
-SELECT id, c FROM t1 WHERE c = 300;
+SELECT id, c FROM t_ddl WHERE c = 300;
 
 --echo # ---- INPLACE: add + drop in one statement ----
-ALTER TABLE t1 ADD INDEX idx_a2 (a), DROP INDEX idx_c, ALGORITHM=INPLACE;
-SHOW INDEX FROM t1;
-EXPLAIN SELECT id, a FROM t1 WHERE a = 20;
-SELECT id, a FROM t1 WHERE a = 20;
+ALTER TABLE t_ddl ADD INDEX idx_a2 (a), DROP INDEX idx_c, ALGORITHM=INPLACE;
+SHOW INDEX FROM t_ddl;
+EXPLAIN SELECT id, a FROM t_ddl WHERE a = 20;
+SELECT id, a FROM t_ddl WHERE a = 20;
 
 --echo # ---- COPY fallback: add column ----
-ALTER TABLE t1 ADD COLUMN d INT DEFAULT 0;
-SELECT id, d FROM t1 WHERE id = 1;
+ALTER TABLE t_ddl ADD COLUMN d INT DEFAULT 0;
+SELECT id, d FROM t_ddl WHERE id = 1;
 
 --echo # ---- COPY fallback: drop column ----
-ALTER TABLE t1 DROP COLUMN d;
-SELECT * FROM t1 WHERE id = 1;
+ALTER TABLE t_ddl DROP COLUMN d;
+SELECT * FROM t_ddl WHERE id = 1;
 
 --echo # ---- Verify ALGORITHM=INPLACE rejected for column changes ----
 --error ER_ALTER_OPERATION_NOT_SUPPORTED
-ALTER TABLE t1 ADD COLUMN e INT, ALGORITHM=INPLACE;
+ALTER TABLE t_ddl ADD COLUMN e INT, ALGORITHM=INPLACE;
 
 --echo # ---- Cleanup ----
-DROP TABLE t1;
+DROP TABLE t_ddl;
 
 --echo # ---- Test with data and hidden PK (no explicit PK) ----
 CREATE TABLE t_nopk (
@@ -90,3 +90,22 @@ SELECT a, b FROM t_nopk WHERE a = 2;
 ALTER TABLE t_nopk DROP INDEX idx_a, ALGORITHM=INPLACE;
 
 DROP TABLE t_nopk;
+
+--echo # ---- ADD UNIQUE must reject duplicates ----
+CREATE TABLE t_dup (
+  i INT NOT NULL,
+  j INT NOT NULL DEFAULT 0
+) ENGINE=TidesDB;
+
+INSERT INTO t_dup VALUES (1, 0);
+INSERT INTO t_dup VALUES (2, 0);
+SELECT * FROM t_dup ORDER BY i;
+
+--error ER_DUP_ENTRY
+ALTER TABLE t_dup ADD UNIQUE unq_j (j);
+
+# Both rows must still be present after the failed ALTER
+SELECT * FROM t_dup ORDER BY i;
+SELECT COUNT(*) FROM t_dup;
+
+DROP TABLE t_dup;
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_stress.test b/mysql-test/suite/tidesdb/t/tidesdb_stress.test
index 31296f5..42b3b86 100644
--- a/mysql-test/suite/tidesdb/t/tidesdb_stress.test
+++ b/mysql-test/suite/tidesdb/t/tidesdb_stress.test
@@ -501,20 +501,25 @@ COMMIT;
 
 --echo #
 --echo # ============================================
---echo # TEST 19: Duplicate PK insert in transaction (upsert semantics)
---echo #   TidesDB uses KV put-overwrites, so a duplicate PK INSERT
---echo #   acts as an upsert.  Verify the txn continues and the
---echo #   last write wins.
+--echo # TEST 19: PK uniqueness enforcement and REPLACE INTO
+--echo #   Duplicate PK INSERT must return an error.
+--echo #   REPLACE INTO overwrites the existing row.
 --echo # ============================================
 --echo #
 
 CREATE TABLE stress_uniq (id INT PRIMARY KEY, val VARCHAR(50)) ENGINE=TIDESDB;
 INSERT INTO stress_uniq VALUES (1, 'first');
 
+# Duplicate PK INSERT must fail
+--error ER_DUP_ENTRY
+INSERT INTO stress_uniq VALUES (1, 'should_fail');
+
+# REPLACE INTO should overwrite
+REPLACE INTO stress_uniq VALUES (1, 'replaced');
+
 BEGIN;
 INSERT INTO stress_uniq VALUES (2, 'second');
-# Duplicate PK -- TidesDB overwrites (upsert), no error
-INSERT INTO stress_uniq VALUES (1, 'overwritten');
+REPLACE INTO stress_uniq VALUES (1, 'overwritten');
 INSERT INTO stress_uniq VALUES (3, 'third');
 COMMIT;
 
diff --git a/mysql-test/suite/tidesdb/t/tidesdb_ttl.test b/mysql-test/suite/tidesdb/t/tidesdb_ttl.test
index 430d452..6491426 100644
--- a/mysql-test/suite/tidesdb/t/tidesdb_ttl.test
+++ b/mysql-test/suite/tidesdb/t/tidesdb_ttl.test
@@ -142,6 +142,98 @@ SHOW CREATE TABLE t_ttl_show;
 
 DROP TABLE t_ttl_show;
 
+--echo #
+--echo # ============================================
+--echo # TEST 7: Session TTL override (SET SESSION)
+--echo #   Table has no TTL; session variable applies
+--echo # ============================================
+--echo #
+
+CREATE TABLE t_ttl_sess (
+  id INT PRIMARY KEY,
+  val VARCHAR(50)
+) ENGINE=TIDESDB;
+
+--echo # Default session TTL is 0 (no override)
+SELECT @@session.tidesdb_ttl;
+
+SET SESSION tidesdb_ttl = 2;
+
+INSERT INTO t_ttl_sess VALUES (1, 'session_ttl'), (2, 'also_session');
+
+--echo # Rows visible immediately
+SELECT * FROM t_ttl_sess ORDER BY id;
+
+SET SESSION tidesdb_ttl = 0;
+
+--echo # Wait for session TTL to expire (3s > 2s)
+--sleep 3
+
+--echo # Rows should now be expired
+SELECT * FROM t_ttl_sess ORDER BY id;
+
+DROP TABLE t_ttl_sess;
+
+--echo #
+--echo # ============================================
+--echo # TEST 8: SET STATEMENT tidesdb_ttl=N FOR ...
+--echo #   Only the single statement gets TTL
+--echo # ============================================
+--echo #
+
+CREATE TABLE t_ttl_stmt (
+  id INT PRIMARY KEY,
+  val VARCHAR(50)
+) ENGINE=TIDESDB;
+
+# Row 1: inserted with 2-second TTL via SET STATEMENT
+SET STATEMENT tidesdb_ttl=2 FOR
+  INSERT INTO t_ttl_stmt VALUES (1, 'short_lived');
+
+# Row 2: inserted with default (no TTL)
+INSERT INTO t_ttl_stmt VALUES (2, 'permanent');
+
+--echo # Both rows visible immediately
+SELECT * FROM t_ttl_stmt ORDER BY id;
+
+--sleep 3
+
+--echo # Row 1 expired (session TTL=2); row 2 still alive (no TTL)
+SELECT * FROM t_ttl_stmt ORDER BY id;
+
+DROP TABLE t_ttl_stmt;
+
+--echo #
+--echo # ============================================
+--echo # TEST 9: Session TTL does NOT override per-row TTL_COL
+--echo # ============================================
+--echo #
+
+CREATE TABLE t_ttl_priority (
+  id INT PRIMARY KEY,
+  val VARCHAR(50),
+  row_ttl INT `TTL`=1
+) ENGINE=TIDESDB;
+
+SET SESSION tidesdb_ttl = 86400;
+
+# Row 1: per-row TTL=2 should win over session TTL=86400
+INSERT INTO t_ttl_priority VALUES (1, 'per_row_wins', 2);
+# Row 2: per-row TTL=0 falls back to session TTL=86400
+INSERT INTO t_ttl_priority VALUES (2, 'uses_session', 0);
+
+SET SESSION tidesdb_ttl = 0;
+
+--echo # Both visible immediately
+SELECT id, val FROM t_ttl_priority ORDER BY id;
+
+--sleep 3
+
+--echo # Row 1 expired (per-row TTL=2 wins); row 2 still alive (session TTL=86400)
+SELECT id, val FROM t_ttl_priority ORDER BY id;
+
+DROP TABLE t_ttl_priority;
+
 --echo #
 --echo #
 --echo # Done.
diff --git a/tidesdb/ha_tidesdb.cc b/tidesdb/ha_tidesdb.cc
index 522a43c..32987c1 100644
--- a/tidesdb/ha_tidesdb.cc
+++ b/tidesdb/ha_tidesdb.cc
@@ -19,6 +19,7 @@
 #include <mysql/plugin.h>
 
 #include <cstring>
+#include <set>
 #include <string>
 #include <vector>
 
@@ -43,6 +44,14 @@ static inline long long tdb_now_us()
     return (long long)microsecond_interval_timer();
 }
 
+/* MariaDB 12.3 moved option_struct from TABLE_SHARE to TABLE (MDEV-37815).
+   We provide a compat macro so the same code compiles on 11.x / 12.0-12.2 / 12.3+. */
+#if MYSQL_VERSION_ID >= 120300
+#define TDB_TABLE_OPTIONS(tbl) ((tbl)->option_struct)
+#else
+#define TDB_TABLE_OPTIONS(tbl) ((tbl)->s->option_struct)
+#endif
+
 /* Declared early so tdb_rc_to_ha() can reference it; default 0,
    toggled at runtime via SET GLOBAL tidesdb_debug_trace. */
 static my_bool srv_debug_trace = 0;
@@ -127,8 +136,16 @@ static ulonglong srv_block_cache_size = TIDESDB_DEFAULT_BLOCK_CACHE; /* 256MB */
 static ulong srv_max_open_sstables = 256;
 static ulonglong srv_max_memory_usage = 0; /* 0 = auto (library decides) */
 
+/* Per-session TTL override (seconds).  0 = use table default. */
+static MYSQL_THDVAR_ULONGLONG(ttl, PLUGIN_VAR_RQCMDARG,
+                              "Per-session TTL in seconds applied to INSERT/UPDATE; "
+                              "0 means use the table-level TTL option; "
+                              "can be set with SET [SESSION] tidesdb_ttl=N or "
+                              "SET STATEMENT tidesdb_ttl=N FOR INSERT",
+                              NULL, NULL, 0, 0, ULONGLONG_MAX, 0);
+
 static const char *log_level_names[] = {"DEBUG", "INFO", "WARN", "ERROR", "FATAL", "NONE", NullS};
-#if MYSQL_VERSION_ID >= 120000
+#if MYSQL_VERSION_ID >= 110800
 static TYPELIB log_level_typelib = {array_elements(log_level_names) - 1, "log_level_typelib",
                                     log_level_names, NULL, NULL};
 #else
@@ -221,6 +238,7 @@ static struct st_mysql_sys_var *tidesdb_system_variables[] = {MYSQL_SYSVAR(flush
                                                               MYSQL_SYSVAR(max_memory_usage),
                                                               MYSQL_SYSVAR(backup_dir),
                                                               MYSQL_SYSVAR(debug_trace),
+                                                              MYSQL_SYSVAR(ttl),
                                                               NULL};
 
 /* ******************** Table options (per-table CF config) ******************** */
@@ -424,6 +442,7 @@ static tidesdb_trx_t *get_or_create_trx(THD *thd, handlerton *hton, tidesdb_isol
             }
             trx->dirty = false;
             trx->isolation_level = iso;
+            trx->txn_generation++;
         }
         return trx;
     }
@@ -440,6 +459,7 @@ static tidesdb_trx_t *get_or_create_trx(THD *thd, handlerton *hton, tidesdb_isol
     }
     trx->dirty = false;
     trx->isolation_level = iso;
+    trx->txn_generation = 1;
     thd_set_ha_data(thd, hton, trx);
     return trx;
 }
@@ -504,7 +524,7 @@ static int tidesdb_savepoint_release(THD *thd, void *sv)
     return tdb_rc_to_ha(rc, "savepoint_release");
 }
 
-#if MYSQL_VERSION_ID >= 120000
+#if MYSQL_VERSION_ID >= 110800
 static int tidesdb_commit(THD *thd, bool all)
 #else
 static int tidesdb_commit(handlerton *, THD *thd, bool all)
@@ -585,7 +605,7 @@ static int tidesdb_commit(handlerton *, THD *thd, bool all)
     return 0;
 }
 
-#if MYSQL_VERSION_ID >= 120000
+#if MYSQL_VERSION_ID >= 110800
 static int tidesdb_rollback(THD *thd, bool all)
 #else
 static int tidesdb_rollback(handlerton *, THD *thd, bool all)
@@ -629,7 +649,7 @@ static int tidesdb_rollback(handlerton *, THD *thd, bool all)
     return 0;
 }
 
-#if MYSQL_VERSION_ID >= 120000
+#if MYSQL_VERSION_ID >= 110800
 static int tidesdb_close_connection(THD *thd)
 #else
 static int tidesdb_close_connection(handlerton *, THD *thd)
@@ -649,8 +669,29 @@ static int tidesdb_close_connection(handlerton *, THD *thd)
     return 0;
 }
 
+/*
+  START TRANSACTION WITH CONSISTENT SNAPSHOT callback.
+  Eagerly creates a TidesDB transaction with REPEATABLE_READ isolation
+  so the snapshot sequence number is captured now, not lazily at first
+  data access.  Without this, rows committed by other connections between
+  START TRANSACTION and the first SELECT would be visible.
+*/
+static int tidesdb_start_consistent_snapshot(THD *thd)
+{
+    tidesdb_trx_t *trx = get_or_create_trx(thd, tidesdb_hton, TDB_ISOLATION_REPEATABLE_READ);
+    if (!trx) return 1;
+
+    /* Register at both statement and transaction level so the server
+       knows TidesDB is participating in this BEGIN block. */
+    trans_register_ha(thd, false, tidesdb_hton, 0);
+    trans_register_ha(thd, true, tidesdb_hton, 0);
+    return 0;
+}
+
 /* ******************** Plugin init / deinit ******************** */
 
+static int tidesdb_hton_drop_table(handlerton *, const char *path);
+
 static int tidesdb_init_func(void *p)
 {
     DBUG_ENTER("tidesdb_init_func");
@@ -662,7 +703,7 @@ static int tidesdb_init_func(void *p)
     tidesdb_hton->tablefile_extensions = ha_tidesdb_exts;
     tidesdb_hton->table_options = tidesdb_table_option_list;
     tidesdb_hton->field_options = tidesdb_field_option_list;
-    tidesdb_hton->drop_table = [](handlerton *, const char *) { return -1; };
+    tidesdb_hton->drop_table = tidesdb_hton_drop_table;
 
     /* Handlerton transaction callbacks -- one TidesDB txn per BEGIN..COMMIT */
     tidesdb_hton->commit = tidesdb_commit;
@@ -673,6 +714,7 @@ static int tidesdb_init_func(void *p)
     tidesdb_hton->savepoint_rollback = tidesdb_savepoint_rollback;
     tidesdb_hton->savepoint_rollback_can_release_mdl = tidesdb_savepoint_rollback_can_release_mdl;
     tidesdb_hton->savepoint_release = tidesdb_savepoint_release;
+    tidesdb_hton->start_consistent_snapshot = tidesdb_start_consistent_snapshot;
 
     tidesdb_init(NULL, NULL, NULL, NULL);
 
@@ -782,7 +824,8 @@ ha_tidesdb::ha_tidesdb(handlerton *hton, TABLE_SHARE *table_arg)
       idx_search_comp_len_(0),
       in_bulk_insert_(false),
       bulk_insert_ops_(0),
-      keyread_only_(false)
+      keyread_only_(false),
+      write_can_replace_(false)
 {
 }
 
@@ -1352,24 +1395,24 @@ int ha_tidesdb::open(const char *name, int mode, uint test_if_locked)
         }
 
         /* We read isolation level from table options */
-        if (table->s->option_struct)
+        if (TDB_TABLE_OPTIONS(table))
         {
-            uint iso_idx = table->s->option_struct->isolation_level;
+            uint iso_idx = TDB_TABLE_OPTIONS(table)->isolation_level;
             if (iso_idx < array_elements(tdb_isolation_map))
                 share->isolation_level = (tidesdb_isolation_level_t)tdb_isolation_map[iso_idx];
         }
 
         /* We read TTL configuration from table + field options */
-        if (table->s->option_struct) share->default_ttl = table->s->option_struct->ttl;
+        if (TDB_TABLE_OPTIONS(table)) share->default_ttl = TDB_TABLE_OPTIONS(table)->ttl;
 
         /* We read encryption configuration from table options */
         share->encrypted = false;
         share->encryption_key_id = 1;
         share->encryption_key_version = 0;
-        if (table->s->option_struct && table->s->option_struct->encrypted)
+        if (TDB_TABLE_OPTIONS(table) && TDB_TABLE_OPTIONS(table)->encrypted)
         {
             share->encrypted = true;
-            share->encryption_key_id = (uint)table->s->option_struct->encryption_key_id;
+            share->encryption_key_id = (uint)TDB_TABLE_OPTIONS(table)->encryption_key_id;
             uint ver = encryption_key_get_latest_version(share->encryption_key_id);
             if (ver == ENCRYPTION_KEY_VERSION_INVALID)
             {
@@ -1429,6 +1472,14 @@ int ha_tidesdb::open(const char *name, int mode, uint test_if_locked)
 
         /* We recover hidden-PK counter (auto-inc is derived at runtime via index_last) */
         recover_counters();
+
+        /* We seed create_time from the .frm file's mtime */
+        {
+            char frm_path[FN_REFLEN];
+            fn_format(frm_path, name, "", reg_ext, MY_UNPACK_FILENAME | MY_APPEND_EXT);
+            MY_STAT st_buf;
+            if (mysql_file_stat(0, frm_path, &st_buf, MYF(0))) share->create_time = st_buf.st_mtime;
+        }
     }
     unlock_shared_ha_data();
 
@@ -1464,7 +1515,7 @@ int ha_tidesdb::create(const char *name, TABLE *table_arg, HA_CREATE_INFO *creat
 
     std::string cf_name = path_to_cf_name(name);
 
-    ha_table_option_struct *opts = table_arg->s->option_struct;
+    ha_table_option_struct *opts = TDB_TABLE_OPTIONS(table_arg);
     DBUG_ASSERT(opts);
 
     tidesdb_column_family_config_t cfg = build_cf_config(opts);
@@ -1744,6 +1795,14 @@ time_t ha_tidesdb::compute_row_ttl(const uchar *buf)
         }
     }
 
+    /* Session TTL override (SET SESSION tidesdb_ttl=N) takes precedence
+       over the table-level default but not over per-row TTL_COL. */
+    if (ttl_seconds <= 0)
+    {
+        ulonglong sess = THDVAR(ha_thd(), ttl);
+        if (sess > 0) ttl_seconds = (long long)sess;
+    }
+
     if (ttl_seconds <= 0 && share->default_ttl > 0) ttl_seconds = (long long)share->default_ttl;
 
     if (ttl_seconds <= 0) return TIDESDB_TTL_NONE;
@@ -1884,8 +1943,64 @@ int ha_tidesdb::write_row(const uchar *buf)
         t2 = tdb_now_us();
     }
 
-    /* We compute TTL only when the table has TTL configured */
-    time_t row_ttl = share->has_ttl ? compute_row_ttl(buf) : TIDESDB_TTL_NONE;
+    /* We check PK uniqueness before inserting (TidesDB put overwrites silently).
+       Skip when REPLACE INTO or INSERT ON DUPLICATE KEY UPDATE -- the server
+       handles the conflict by deleting the old row first (HA_EXTRA_WRITE_CAN_REPLACE). */
+    if (share->has_user_pk && !write_can_replace_)
+    {
+        uint8_t *dup_val = NULL;
+        size_t dup_len = 0;
+        int grc = tidesdb_txn_get(txn, share->cf, dk, dk_len, &dup_val, &dup_len);
+        if (grc == TDB_SUCCESS)
+        {
+            tidesdb_free(dup_val);
+            errkey = lookup_errkey = share->pk_index;
+            tmp_restore_column_map(&table->read_set, old_map);
+            DBUG_RETURN(HA_ERR_FOUND_DUPP_KEY);
+        }
+        if (grc != TDB_ERR_NOT_FOUND)
+        {
+            tmp_restore_column_map(&table->read_set, old_map);
+            DBUG_RETURN(tdb_rc_to_ha(grc, "write_row pk_dup_check"));
+        }
+    }
+
+    /* We check UNIQUE secondary index uniqueness via prefix scan */
+    if (share->num_secondary_indexes > 0 && !write_can_replace_)
+    {
+        for (uint i = 0; i < table->s->keys; i++)
+        {
+            if (share->has_user_pk && i == share->pk_index) continue;
+            if (i >= share->idx_cfs.size() || !share->idx_cfs[i]) continue;
+            if (!(table->key_info[i].flags & HA_NOSAME)) continue;
+
+            uchar idx_prefix[MAX_KEY_LENGTH];
+            uint idx_prefix_len = make_comparable_key(
+                &table->key_info[i], buf, table->key_info[i].user_defined_key_parts, idx_prefix);
+            tidesdb_iter_t *dup_iter = NULL;
+            if (tidesdb_iter_new(txn, share->idx_cfs[i], &dup_iter) != TDB_SUCCESS || !dup_iter)
+                continue;
+            tidesdb_iter_seek(dup_iter, idx_prefix, idx_prefix_len);
+            if (tidesdb_iter_valid(dup_iter))
+            {
+                uint8_t *fk = NULL;
+                size_t fks = 0;
+                if (tidesdb_iter_key(dup_iter, &fk, &fks) == TDB_SUCCESS && fks >= idx_prefix_len &&
+                    memcmp(fk, idx_prefix, idx_prefix_len) == 0)
+                {
+                    tidesdb_iter_free(dup_iter);
+                    errkey = lookup_errkey = i;
+                    tmp_restore_column_map(&table->read_set, old_map);
+                    DBUG_RETURN(HA_ERR_FOUND_DUPP_KEY);
+                }
+            }
+            tidesdb_iter_free(dup_iter);
+        }
+    }
+
+    /* We compute TTL when the table has TTL configured or the session overrides it */
+    time_t row_ttl =
+        (share->has_ttl || THDVAR(ha_thd(), ttl) > 0) ? compute_row_ttl(buf) : TIDESDB_TTL_NONE;
 
     /* We insert data row */
     int rc = tidesdb_txn_put(txn, share->cf, dk, dk_len, row_ptr, row_len, row_ttl);
@@ -2012,7 +2127,11 @@ int ha_tidesdb::rnd_init(bool scan)
     }
     scan_txn = stmt_txn;
 
-    if (scan_iter && (scan_iter_cf_ != share->cf || scan_iter_txn_ != scan_txn))
+    tidesdb_trx_t *trx = (tidesdb_trx_t *)thd_get_ha_data(ha_thd(), ht);
+    uint64_t cur_gen = trx ? trx->txn_generation : 0;
+
+    if (scan_iter &&
+        (scan_iter_cf_ != share->cf || scan_iter_txn_ != scan_txn || scan_iter_txn_gen_ != cur_gen))
     {
         tidesdb_iter_free(scan_iter);
         scan_iter = NULL;
@@ -2030,6 +2149,7 @@ int ha_tidesdb::rnd_init(bool scan)
         }
         scan_iter_cf_ = share->cf;
         scan_iter_txn_ = scan_txn;
+        scan_iter_txn_gen_ = cur_gen;
     }
 
     /* We seek past meta keys to the first data key */
@@ -2125,11 +2245,18 @@ int ha_tidesdb::index_init(uint idx, bool sorted)
        (each builds a merge heap from all SSTables).
 
        If the txn changed (e.g. after COMMIT created a new one), the
-       iterator holds a stale txn pointer and must be recreated. */
-    if (scan_iter && (scan_iter_cf_ != target_cf || scan_iter_txn_ != scan_txn))
-    {
-        TDB_TRACE("idx=%u iter INVALIDATED (cf %p->%p txn %p->%p)", idx, scan_iter_cf_, target_cf,
-                  scan_iter_txn_, scan_txn);
+       iterator holds a stale txn pointer and must be recreated.
+       We compare both the pointer and a monotonic generation counter
+       because the allocator can reuse the same address for a new txn. */
+    tidesdb_trx_t *trx = (tidesdb_trx_t *)thd_get_ha_data(ha_thd(), ht);
+    uint64_t cur_gen = trx ? trx->txn_generation : 0;
+
+    if (scan_iter &&
+        (scan_iter_cf_ != target_cf || scan_iter_txn_ != scan_txn || scan_iter_txn_gen_ != cur_gen))
+    {
+        TDB_TRACE("idx=%u iter INVALIDATED (cf %p->%p txn %p->%p gen %lu->%lu)", idx, scan_iter_cf_,
+                  target_cf, scan_iter_txn_, scan_txn, (unsigned long)scan_iter_txn_gen_,
+                  (unsigned long)cur_gen);
         tidesdb_iter_free(scan_iter);
         scan_iter = NULL;
         scan_iter_cf_ = NULL;
@@ -2157,6 +2284,8 @@ int ha_tidesdb::ensure_scan_iter()
     {
         scan_iter_cf_ = scan_cf_;
         scan_iter_txn_ = scan_txn;
+        tidesdb_trx_t *trx = (tidesdb_trx_t *)thd_get_ha_data(ha_thd(), ht);
+        scan_iter_txn_gen_ = trx ? trx->txn_generation : 0;
         return 0;
     }
     return tdb_rc_to_ha(rc, "ensure_scan_iter");
@@ -2771,8 +2900,9 @@ int ha_tidesdb::update_row(const uchar *old_data, const uchar *new_data)
     int rc;
     bool pk_changed = (old_pk_len != new_pk_len || memcmp(old_pk, new_pk, old_pk_len) != 0);
 
-    /* We compute TTL only when the table has TTL configured */
-    time_t row_ttl = share->has_ttl ? compute_row_ttl(new_data) : TIDESDB_TTL_NONE;
+    /* We compute TTL when the table has TTL configured or the session overrides it */
+    time_t row_ttl = (share->has_ttl || THDVAR(ha_thd(), ttl) > 0) ? compute_row_ttl(new_data)
+                                                                   : TIDESDB_TTL_NONE;
 
     /* If PK changed, we delete old entry and insert new */
     if (pk_changed)
@@ -2934,7 +3064,7 @@ int ha_tidesdb::delete_all_rows(void)
         stmt_txn_dirty = false;
     }
 
-    tidesdb_column_family_config_t cfg = build_cf_config(table->s->option_struct);
+    tidesdb_column_family_config_t cfg = build_cf_config(TDB_TABLE_OPTIONS(table));
 
     /* We drop and recreate the main data CF (O(1) instead of iterating all keys) */
     {
@@ -3042,7 +3172,16 @@ int ha_tidesdb::info(uint flag)
             if (tidesdb_get_stats(share->cf, &st) == TDB_SUCCESS && st)
             {
                 share->cached_records.store(st->total_keys, std::memory_order_relaxed);
-                share->cached_data_size.store(st->total_data_size, std::memory_order_relaxed);
+
+                /* total_data_size only counts SSTable klog+vlog; memtable_size
+                   holds the active memtable footprint.  Sum both so that
+                   DATA_LENGTH in information_schema.TABLES is non-zero even
+                   before the first flush.  When both are 0 (library gap),
+                   fall back to total_keys * avg entry size. */
+                uint64_t data_sz = st->total_data_size + (uint64_t)st->memtable_size;
+                if (data_sz == 0 && st->total_keys > 0)
+                    data_sz = (uint64_t)(st->total_keys * (st->avg_key_size + st->avg_value_size));
+                share->cached_data_size.store(data_sz, std::memory_order_relaxed);
                 uint32_t mrl = (uint32_t)(st->avg_key_size + st->avg_value_size);
                 if (mrl == 0) mrl = table->s->reclength;
                 share->cached_mean_rec_len.store(mrl, std::memory_order_relaxed);
@@ -3057,7 +3196,11 @@ int ha_tidesdb::info(uint flag)
                     tidesdb_stats_t *ist = NULL;
                     if (tidesdb_get_stats(share->idx_cfs[i], &ist) == TDB_SUCCESS && ist)
                     {
-                        idx_total += ist->total_data_size;
+                        uint64_t isz = ist->total_data_size + (uint64_t)ist->memtable_size;
+                        if (isz == 0 && ist->total_keys > 0)
+                            isz = (uint64_t)(ist->total_keys *
+                                             (ist->avg_key_size + ist->avg_value_size));
+                        idx_total += isz;
                         tidesdb_free_stats(ist);
                     }
                 }
@@ -3078,6 +3221,13 @@ int ha_tidesdb::info(uint flag)
         stats.mrr_length_per_rec = ref_length + 8;
     }
 
+    /* HA_STATUS_TIME -- create_time from .frm stat, update_time from last DML */
+    if ((flag & HA_STATUS_TIME) && share)
+    {
+        stats.create_time = share->create_time;
+        stats.update_time = share->update_time.load(std::memory_order_relaxed);
+    }
+
     /* HA_STATUS_CONST       -- set rec_per_key for index selectivity estimates.
        For PK (unique)       -- rec_per_key = 1.
        For secondary indexes -- we estimate from total_keys / distinct count.
@@ -3404,6 +3554,13 @@ int ha_tidesdb::extra(enum ha_extra_function operation)
         case HA_EXTRA_NO_KEYREAD:
             keyread_only_ = false;
             break;
+        case HA_EXTRA_WRITE_CAN_REPLACE:
+        case HA_EXTRA_INSERT_WITH_UPDATE:
+            write_can_replace_ = true;
+            break;
+        case HA_EXTRA_WRITE_CANNOT_REPLACE:
+            write_can_replace_ = false;
+            break;
         case HA_EXTRA_PREPARE_FOR_DROP:
             /* Table is about to be dropped -- skip fsync overhead */
             break;
@@ -3433,6 +3590,13 @@ int ha_tidesdb::ensure_stmt_txn()
     bool in_multi_stmt_txn = thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN);
     tidesdb_isolation_level_t effective_iso =
         in_multi_stmt_txn ? share->isolation_level : TDB_ISOLATION_READ_COMMITTED;
+
+    /* Force READ_COMMITTED for DDL to avoid unbounded read-set growth */
+    int sql_cmd = thd_sql_command(thd);
+    if (sql_cmd == SQLCOM_ALTER_TABLE || sql_cmd == SQLCOM_CREATE_INDEX ||
+        sql_cmd == SQLCOM_DROP_INDEX || sql_cmd == SQLCOM_TRUNCATE || sql_cmd == SQLCOM_OPTIMIZE ||
+        sql_cmd == SQLCOM_CREATE_TABLE || sql_cmd == SQLCOM_DROP_TABLE)
+        effective_iso = TDB_ISOLATION_READ_COMMITTED;
     tidesdb_trx_t *trx = get_or_create_trx(thd, ht, effective_iso);
     if (!trx) return HA_ERR_OUT_OF_MEM;
 
@@ -3461,10 +3625,26 @@ int ha_tidesdb::external_lock(THD *thd, int lock_type)
 
            For multi-statement transactions (BEGIN...COMMIT) we keep
            the table's configured isolation level so that application-
-           level retry logic handles the (rare) OCC conflicts. */
+           level retry logic handles the (rare) OCC conflicts.
+
+           DDL operations (ALTER TABLE, CREATE/DROP INDEX, TRUNCATE,
+           OPTIMIZE, etc.) always use READ_COMMITTED regardless of
+           transaction context.  The copy-based ALTER TABLE scan can
+           read hundreds of thousands of rows; REPEATABLE_READ would
+           add each key to the read-set for conflict detection,
+           causing unbounded memory growth and heap corruption
+           (issue #70).  DDL never needs OCC conflict checks. */
         bool in_multi_stmt_txn = thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN);
         tidesdb_isolation_level_t effective_iso =
             in_multi_stmt_txn ? share->isolation_level : TDB_ISOLATION_READ_COMMITTED;
+
+        /* Force READ_COMMITTED for DDL to avoid unbounded read-set growth */
+        int sql_cmd = thd_sql_command(thd);
+        if (sql_cmd == SQLCOM_ALTER_TABLE || sql_cmd == SQLCOM_CREATE_INDEX ||
+            sql_cmd == SQLCOM_DROP_INDEX || sql_cmd == SQLCOM_TRUNCATE ||
+            sql_cmd == SQLCOM_OPTIMIZE || sql_cmd == SQLCOM_CREATE_TABLE ||
+            sql_cmd == SQLCOM_DROP_TABLE)
+            effective_iso = TDB_ISOLATION_READ_COMMITTED;
         tidesdb_trx_t *trx = get_or_create_trx(thd, ht, effective_iso);
         if (!trx) DBUG_RETURN(HA_ERR_OUT_OF_MEM);
 
@@ -3522,6 +3702,9 @@ int ha_tidesdb::external_lock(THD *thd, int lock_type)
             scan_iter_cf_ = NULL;
             scan_iter_txn_ = NULL;
         }
+        /* We bump update_time once per write-statement for information_schema */
+        if (stmt_txn_dirty && share) share->update_time.store(time(0), std::memory_order_relaxed);
+
         stmt_txn = NULL;
         stmt_txn_dirty = false;
     }
@@ -3609,7 +3792,7 @@ bool ha_tidesdb::prepare_inplace_alter_table(TABLE *altered_table,
     }
     ha_alter_info->handler_ctx = ctx;
 
-    tidesdb_column_family_config_t cfg = build_cf_config(table->s->option_struct);
+    tidesdb_column_family_config_t cfg = build_cf_config(TDB_TABLE_OPTIONS(table));
 
     std::string base_cf = share->cf_name;
 
@@ -3722,6 +3905,17 @@ bool ha_tidesdb::inplace_alter_table(TABLE *altered_table, Alter_inplace_info *h
 
     ha_rows rows_processed = 0;
 
+    /* For UNIQUE indexes, we track seen index-column prefixes to detect
+       duplicates.  If a duplicate is found we must abort the ALTER. */
+    std::vector<bool> idx_is_unique(ctx->add_cfs.size(), false);
+    std::vector<std::set<std::string>> idx_seen(ctx->add_cfs.size());
+    for (uint a = 0; a < ctx->add_cfs.size(); a++)
+    {
+        uint key_num = ctx->add_key_nums[a];
+        KEY *ki = &altered_table->key_info[key_num];
+        if (ki->flags & HA_NOSAME) idx_is_unique[a] = true;
+    }
+
     /* We remember the last data key so we can seek directly to it after
        a batch commit, instead of walking from the beginning (O(n²)). */
     uchar last_data_key[MAX_KEY_LENGTH + 2];
@@ -3800,6 +3994,22 @@ bool ha_tidesdb::inplace_alter_table(TABLE *altered_table, Alter_inplace_info *h
                 pos += kp->length;
                 if (field->real_maybe_null()) pos++;
             }
+            /* Check UNIQUE constraint before inserting */
+            if (idx_is_unique[a])
+            {
+                std::string prefix((const char *)ik, pos);
+                if (!idx_seen[a].insert(prefix).second)
+                {
+                    /* Duplicate found -- abort the ALTER */
+                    tidesdb_iter_free(iter);
+                    tidesdb_txn_rollback(txn);
+                    tidesdb_txn_free(txn);
+                    tmp_restore_column_map(&altered_table->read_set, old_map);
+                    my_error(ER_DUP_ENTRY, MYF(0), "?", altered_table->key_info[key_num].name.str);
+                    DBUG_RETURN(true);
+                }
+            }
+
             /* We append PK to make the key unique */
             memcpy(ik + pos, pk, pk_len);
             pos += pk_len;
@@ -4058,11 +4268,17 @@ static void force_remove_cf_dir(const std::string &cf_name)
         TDB_TRACE("force-removed stale CF dir %s", dir);
 }
 
-int ha_tidesdb::delete_table(const char *name)
+/*
+  Shared drop logic used by both the handlerton callback (hton->drop_table)
+  and the handler method (ha_tidesdb::delete_table).  Drops the main data CF
+  and all secondary index CFs, then force-removes their directories.
+  Returns 0 on success.
+*/
+static int tidesdb_drop_table_impl(const char *path)
 {
-    DBUG_ENTER("ha_tidesdb::delete_table");
+    if (!tdb_global) return 0;
 
-    std::string cf_name = path_to_cf_name(name);
+    std::string cf_name = ha_tidesdb::path_to_cf_name(path);
 
     /* We collect secondary index CF names before dropping so we can
        force-remove their directories afterwards. */
@@ -4088,7 +4304,7 @@ int ha_tidesdb::delete_table(const char *name)
     if (rc != TDB_SUCCESS && rc != TDB_ERR_NOT_FOUND)
     {
         sql_print_error("TIDESDB: Failed to drop CF '%s' (err=%d)", cf_name.c_str(), rc);
-        DBUG_RETURN(tdb_rc_to_ha(rc, "delete_table"));
+        return rc;
     }
 
     for (const auto &idx_name : idx_cf_names)
@@ -4102,7 +4318,22 @@ int ha_tidesdb::delete_table(const char *name)
     force_remove_cf_dir(cf_name);
     for (const auto &idx_name : idx_cf_names) force_remove_cf_dir(idx_name);
 
-    DBUG_RETURN(0);
+    return 0;
+}
+
+/*
+  Handlerton-level drop_table callback.  MariaDB 12.x calls hton->drop_table
+  instead of handler::delete_table.  Must return 0 on success, not -1.
+*/
+static int tidesdb_hton_drop_table(handlerton *, const char *path)
+{
+    return tidesdb_drop_table_impl(path);
+}
+
+int ha_tidesdb::delete_table(const char *name)
+{
+    DBUG_ENTER("ha_tidesdb::delete_table");
+    DBUG_RETURN(tidesdb_drop_table_impl(name));
 }
 
 /* ******************** Plugin declaration ******************** */
@@ -4118,8 +4349,8 @@ maria_declare_plugin(tidesdb){
     PLUGIN_LICENSE_GPL,
     tidesdb_init_func,
     tidesdb_deinit_func,
-    0x30305,
+    0x30306,
     NULL,
     tidesdb_system_variables,
-    "3.3.5",
+    "3.3.6",
     MariaDB_PLUGIN_MATURITY_EXPERIMENTAL} maria_declare_plugin_end;
diff --git a/tidesdb/ha_tidesdb.h b/tidesdb/ha_tidesdb.h
index 48dde57..14c1789 100644
--- a/tidesdb/ha_tidesdb.h
+++ b/tidesdb/ha_tidesdb.h
@@ -117,6 +117,10 @@ class TidesDB_share : public Handler_share
     bool has_ttl;               /* true when TTL is configured (default_ttl or ttl_field_idx) */
     uint num_secondary_indexes; /* count of non-NULL secondary index CFs */
 
+    /* Table timestamps for information_schema.TABLES */
+    time_t create_time{0};              /* from .frm stat at first open */
+    std::atomic<time_t> update_time{0}; /* bumped on DML (write/update/delete) */
+
     /* Cached stats -- avoid expensive tidesdb_get_stats per statement.
        Refreshed at most every 2 seconds; read with relaxed atomics. */
     std::atomic<ha_rows> cached_records{0};
@@ -170,6 +174,7 @@ struct tidesdb_trx_t
     bool stmt_savepoint_active;                /* true while a "stmt" savepoint exists */
     bool stmt_was_dirty;                       /* true if current stmt had writes */
     tidesdb_isolation_level_t isolation_level; /* from first table opened */
+    uint64_t txn_generation; /* monotonic counter; incremented each time a new txn is created */
 };
 
 /*
@@ -190,6 +195,7 @@ class ha_tidesdb : public handler
     tidesdb_column_family_t *scan_cf_;      /* CF for lazy iterator creation */
     tidesdb_column_family_t *scan_iter_cf_; /* CF the cached scan_iter was created for */
     tidesdb_txn_t *scan_iter_txn_;          /* txn the cached scan_iter was created on */
+    uint64_t scan_iter_txn_gen_;            /* txn_generation when scan_iter was created */
     bool idx_pk_exact_done_;                /* deferred seek after PK exact */
     enum scan_dir_t
     {
@@ -217,6 +223,7 @@ class ha_tidesdb : public handler
 
     /* Covering-index mode (HA_EXTRA_KEYREAD) */
     bool keyread_only_;
+    bool write_can_replace_; /* true during REPLACE INTO / INSERT ON DUPLICATE KEY UPDATE */
 
     /* ----- private helpers ----------------------------------------------------------------------
      */
@@ -225,8 +232,6 @@ class ha_tidesdb : public handler
     const std::string &serialize_row(const uchar *buf);
     void deserialize_row(uchar *buf, const uchar *data, size_t len);
     void deserialize_row(uchar *buf, const std::string &row);
-    static std::string path_to_cf_name(const char *path);
-
     /* Build memcmp-comparable key bytes into out[]; returns byte count */
     uint make_comparable_key(KEY *key_info, const uchar *record, uint num_parts, uchar *out);
 
@@ -342,6 +347,9 @@ class ha_tidesdb : public handler
         return cost;
     }
 
+    /* Convert a MariaDB table path to a TidesDB column family name */
+    static std::string path_to_cf_name(const char *path);
+
     /* DDL */
     int open(const char *name, int mode, uint test_if_locked) override;
     int close(void) override;