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SQL Reference & Execution

MiniDB supports a subset of SQL for data manipulation and definition.

Supported Syntax

Data Definition

MiniDB currently creates schemas programmatically in main.go for the users table. Dynamic CREATE TABLE via SQL is not yet exposed in the parser. Schema for users: id (int), name (string).

Data Manipulation

INSERT

INSERT INTO users VALUES (1, 'alice')
INSERT INTO users VALUES (2, 'bob'), (3, 'charlie')

SELECT

SELECT * FROM users
SELECT * FROM users WHERE id = 1
SELECT * FROM users WHERE name = 'alice'
  • SELECT * is the only projected column set supported.
  • WHERE supports simple equality checks (=).

Maintenance Commands

These are custom extensions to manage the storage engine.

FLUSH    -- Flushes MemTable to Disk (SSTable)
COMPACT  -- Merges all SSTables

Transaction Control

BEGIN
COMMIT
ROLLBACK (or ABORT)

Execution Flow

  1. Parser: The custom recursive-descent parser (internal/sql/parser) reads the SQL string.

    • If valid, returns a Statement node (e.g., SelectStmt).
    • If invalid, returns a syntax error.

  2. Binder: The binder (internal/sql/binder) resolves table and column names against the Catalog.

    • It converts Statement (AST) -> LogicalPlan.
    • Optimization: If a WHERE clause references an indexed column (e.g., id), the Binder generates an IndexScanNode instead of a SeqScanNode + FilterNode.

  3. Executor: The logic plan is converted into a tree of physical Iterators.

    • Next() is called repeatedly on the root iterator.
    • Each iterator pulls data from its child, processes it (filters, projects), and returns it up the stack.