Fix temporary table lookup without stringified fetches and with a different case

[Nandan108]

Summary

The internal check for whether a table is temporary (temporary_table_exists()) has two defects. It is used by ALTER TABLE, DROP TABLE, SHOW COLUMNS, SHOW CREATE TABLE, DESCRIBE, UPDATE, and others to decide whether to use the temporary or the standard information schema.

1. It compares the fetched value to the string '1'. PDO SQLite returns native types unless PDO::ATTR_STRINGIFY_FETCHES is set, so on PHP 8.1 and newer, the check never finds a temporary table for callers that don't set that attribute. The WordPress plugin and the MySQL proxy set it, so they are unaffected, but the PDO-compatible API is:

   $pdo = new WP_MySQL_On_SQLite( 'mysql-on-sqlite:dbname=wp', ... );
   $pdo->query( 'CREATE TEMPORARY TABLE t (a INT)' );
   $pdo->query( 'ALTER TABLE t ADD COLUMN b INT' );
   // SQLSTATE[42S02]: Base table or view not found: 1146 Table 't' doesn't exist

   When a standard table of the same name exists, the statement silently applies to that table instead.

2. It matches the table name case-sensitively, unlike the information schema tables (COLLATE NOCASE), so a temporary table is not found by a differently cased name:

   CREATE TEMPORARY TABLE t (a INT);
   ALTER TABLE T ADD COLUMN b INT;
   -- SQLSTATE[42S02]: Base table or view not found: 1146 Table 'T' doesn't exist

Fix

The lookup matches the name with COLLATE NOCASE and checks the fetched value for presence (false !== fetchColumn()) rather than comparing it to a string. The translation tests filter this query out of the recorded SQLite statements by its text, so the filter is updated to match.

Queries to the information schema no longer use this lookup with the name of the information schema table, such as columns. Temporary tables are not listed in the information schema, but with a case-insensitive lookup, a temporary table named Columns would hide all standard tables from information_schema.columns.

Tests

• testTemporaryTableHasPriorityOverStandardTable runs with stringified fetches enabled and disabled.
• testTemporaryTableIsFoundByDifferentlyCasedName uses a differently cased name in ALTER TABLE, SHOW COLUMNS, and DROP TABLE while a standard table with the same name exists.
• testTemporaryTableNamedLikeInformationSchemaTable checks that temporary tables named like information schema tables don't change the information schema results.

All three fail on trunk.

Found while preparing a fix for CREATE TEMPORARY TABLE IF NOT EXISTS, which will reuse this lookup.

Part of #451.

Use of AI

This change was prepared with Claude Code (Claude Fable 5.1). I reviewed the code, the tests, and this description, and I take responsibility for the change.

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Summary by CodeRabbit

• Bug Fixes
  • Temporary tables are recognized regardless of capitalization or database fetch format.
  • ALTER TABLE and DROP TABLE correctly target temporary tables when names differ only by capitalization or overlap with a regular table.
  • Temporary tables named after information schema tables no longer appear in those schema results; the corresponding standard tables remain visible. Column listings continue to resolve differently cased references to temporary tables.

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Reviewing files that changed from the base of the PR and between be0bdf8 and 7a8d622.

📒 Files selected for processing (2)

• packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php
• packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Tests.php

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📝 Walkthrough

Temporary-table existence checks now match names without regard to case and accept any fetched value other than false. Table-reference translation always uses the non-temporary information-schema mapping. Tests cover fetch stringification, differently cased references, and temporary tables named like information-schema tables.

Changes: Temporary-table resolution

Layer / File(s)	Summary
Temporary-table lookup and tests packages/mysql-on-sqlite/src/sqlite/class-wp-sqlite-information-schema-builder.php, packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Tests.php, packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Translation_Tests.php	The existence check uses a case-insensitive name match and treats any fetched value other than false as a match. Tests cover differently cased ALTER TABLE and DROP TABLE references, temporary-table priority with both fetch-stringification settings, and the updated query filter.
Information-schema table resolution packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php, packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Tests.php	Table-reference translation always uses the non-temporary information-schema mapping. Tests verify that temporary tables named tables, COLUMNS, or Statistics do not replace matching standard-table metadata.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: janjakes

Merge Risk: ⚪ Minimal · up to 7a8d6

No actionable merge-blocking issue is identified; merge after normal checks.

Pre-merge checks · 4 · 1

Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly summarizes the main change: fixing temporary-table lookup for non-stringified fetches and case differences.

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[JanJakes]

Thanks for the contribution, @Nandan108! The fix looks good.

I pushed two small improvements:

1. Ignore temporary tables named like information schema tables: With the case-insensitive lookup, a temporary table named Columns would hide all standard tables from information_schema.columns.
2. Extend temporary table lookup tests: Covers DROP TABLE with a differently cased name, and runs the priority test with stringified fetches on and off.