Spanner Cassandra ITs - Fix non-idempotent Cassandra schema creation

[darshan-sj]

This PR addresses intermittent AlreadyExistsException failures in Cassandra-based integration tests (specifically CassandraAllDataTypesIT).

Example: https://github.com/GoogleCloudPlatform/DataflowTemplates/actions/runs/22293136720/job/64485274459?pr=3380 https://github.com/GoogleCloudPlatform/DataflowTemplates/actions/runs/22366068580/job/64734193159

The issue stems from the interaction between the CassandraResourceManager's retry policy (via dev.failsafe) and non-idempotent CSQL statements. When Cassandra is under load, a CREATE TABLE statement may succeed on the server but fail to return a response to the client within the timeout window. Failsafe then triggers a retry, which fails immediately because the table was successfully created in the first attempt.

Changes
Updated the CSQL resource files to use IF NOT EXISTS for all CREATE TABLE statements. Ensures that schema setup is idempotent, allowing the CassandraResourceManager to safely retry without failing the test suite.

Unlike CREATE TABLE statements, INSERT statements in Casandra are natively upserts and doesn't cause errors on retry.

[gemini-code-assist]

Summary of Changes

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This pull request enhances the robustness of Cassandra-based integration tests by preventing AlreadyExistsException failures during schema setup. By making table creation idempotent, the system can safely retry operations without encountering errors, thereby improving the stability and reliability of the test suite.

Highlights

• Idempotent Cassandra Schema Creation: Modified all CREATE TABLE statements in Cassandra test schema files to include the IF NOT EXISTS clause, ensuring that table creation operations are idempotent.
• Removed Redundant DROP TABLE Statements: Removed DROP TABLE IF EXISTS statements from cassandra-data-types.csql and cassandra-transformation-schema.sql as they are no longer necessary with idempotent CREATE TABLE.

Changelog

• v2/sourcedb-to-spanner/src/test/resources/DataTypesIT/cassandra-data-types.csql
  • Modified CREATE TABLE all_data_types to include IF NOT EXISTS and removed the preceding DROP TABLE statement.
  • Modified CREATE TABLE "true" to include IF NOT EXISTS.
• v2/spanner-to-sourcedb/src/test/resources/SpannerCassandraReservedKeywordsIT/cassandra-schema.cql
  • Modified CREATE TABLE "true" to include IF NOT EXISTS.
• v2/spanner-to-sourcedb/src/test/resources/SpannerToCassandraSourceIT/cassandra-schema.sql
  • Modified CREATE TABLE users to include IF NOT EXISTS.
  • Modified CREATE TABLE users2 to include IF NOT EXISTS.
  • Modified CREATE TABLE AllDatatypeTransformation to include IF NOT EXISTS.
  • Modified CREATE TABLE AllDatatypeColumns to include IF NOT EXISTS.
  • Modified CREATE TABLE BoundaryConversionTestTable to include IF NOT EXISTS.
  • Modified CREATE TABLE EmptyStringJsonTable to include IF NOT EXISTS.
  • Modified CREATE TABLE testtable_03tpcovf16ed0klxm3v808ch3btgq0uk to include IF NOT EXISTS.
• v2/spanner-to-sourcedb/src/test/resources/SpannerToCassandraSourceIT/cassandra-transformation-schema.sql
  • Modified CREATE TABLE customers to include IF NOT EXISTS and removed the preceding DROP TABLE statement.
• v2/spanner-to-sourcedb/src/test/resources/SpannerToSourceDbWideRowIT/cassandra-10mb-schema.sql
  • Modified CREATE TABLE large_data to include IF NOT EXISTS.

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