Fix temporary table lookup without stringified fetches and with a different case by Nandan108 · Pull Request #522 · WordPress/sqlite-database-integration

Nandan108 · 2026-10-12T16:04:14Z

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.

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.
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.

🤖 Generated with Claude Code

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.

…ferent case The temporary table lookup compared the fetched value to the string "1". PDO SQLite returns native types unless fetches are stringified, so on PHP 8.1 and newer, the lookup never found a temporary table for callers that don't set PDO::ATTR_STRINGIFY_FETCHES. Statements like ALTER TABLE, SHOW COLUMNS, or DESCRIBE then failed or used a standard table of the same name instead. The lookup also matched the table name case-sensitively, unlike the information schema tables, so a temporary table was not found when the statement used a differently cased name. Match the name case-insensitively and check the fetched value for presence rather than comparing it to a string. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

coderabbitai · 2026-10-12T16:04:34Z

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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.

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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.

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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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When translating a reference to an information schema table, the driver checked whether a temporary table with the same name existed, such as "columns". If it did, the query read the temporary table metadata instead of the standard one, so all standard tables disappeared from the result. With the case-insensitive temporary table lookup, any differently cased name triggers this too, e.g., a temporary table named "Columns". Temporary tables are not listed in the information schema, so always read the standard table metadata.

Test the differently cased name with a standard table of the same name, including DROP TABLE. Before the lookup fix, DROP TABLE removed the temporary table, but deleted the metadata of the standard table. Run the temporary table priority test with stringified fetches both enabled and disabled instead of keeping a partial copy of it.

JanJakes · 2026-10-13T13:17:22Z

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

I pushed two small improvements:

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.
Extend temporary table lookup tests: Covers DROP TABLE with a differently cased name, and runs the priority test with stringified fetches on and off.

…532) ## Summary Fixes #451 together with #522. `ALTER TABLE`, `CREATE TABLE`, and `SHOW CREATE TABLE` compare fetched metadata to string values. PDO SQLite returns native types unless `PDO::ATTR_STRINGIFY_FETCHES` is set, so on PHP 8.1 and newer, these comparisons fail 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: ```php $pdo = new WP_MySQL_On_SQLite( 'mysql-on-sqlite:dbname=wp', ... ); $pdo->query( 'CREATE TABLE u (id INT, email VARCHAR(50), UNIQUE KEY ue (email))' ); $pdo->query( "INSERT INTO u VALUES (1, 'a@example.com')" ); $pdo->query( "INSERT INTO u VALUES (2, 'a@example.com')" ); // Accepted: the unique key was created as a plain index. ``` The affected comparisons are the remaining ones listed in #451: - `NON_UNIQUE` is compared to `'0'` when generating the SQLite schema and when generating `SHOW CREATE TABLE` output, so every `UNIQUE KEY` becomes a plain index. That also breaks `INSERT ... ON DUPLICATE KEY UPDATE`, which then inserts duplicates. - `PRAGMA foreign_keys` is compared to `'1'` after `ALTER TABLE` recreates a table, so the foreign key check is skipped. #522 fixes the temporary table lookup, and #506 already fixed schema reconstruction. ## Fix The values are compared as integers. ## Tests `testUniqueKeysWithoutStringifiedFetches` disables stringified fetches, creates a table with a unique key, checks `SHOW CREATE TABLE`, recreates the table with `ALTER TABLE`, and checks that a duplicate row is rejected. It fails on `trunk`. Each of the two `NON_UNIQUE` comparisons fails it separately. The `PRAGMA foreign_keys` comparison has no test. `ALTER TABLE` runs inside the wrapper transaction, where `PRAGMA foreign_keys` is a no-op, so the skipped restore has no observable effect today. It is fixed for consistency. I also ran the whole suite with stringified fetches disabled in every test class. With this PR and #522, the only remaining failures are type differences in returned values (`1` vs `'1'`) and the two tests of the attribute itself. `packages/mysql-on-sqlite`: 1044 tests pass (PHP 8.3, SQLite 3.45.1); PHPCS is clean. ## Use of AI This change was prepared with Claude Code (Claude Opus 5.5). I reviewed the code, the tests, and this description, and I take responsibility for the change. 🤖 Generated with [Claude Code](https://claude.com/claude-code)  ## Summary by CodeRabbit - **Bug Fixes** - Fixed unique database indexes being lost when tables are recreated after a schema change. Duplicate values in uniquely constrained fields are now correctly rejected. - Improved consistency when adding columns to tables: unique constraints are preserved whether database results are returned as strings or other value types. Database table definitions also continue to report unique indexes correctly in either case.  --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Jan Jakeš <jan@jakes.pro>

Nandan108 mentioned this pull request Oct 12, 2026

Fix CREATE TEMPORARY TABLE IF NOT EXISTS and DROP TEMPORARY TABLE as the first temporary table #524

Merged

JanJakes added 2 commits October 13, 2026 15:01

JanJakes merged commit ed86f8b into WordPress:trunk Oct 13, 2026
24 checks passed

Nandan108 mentioned this pull request Oct 13, 2026

Fix unique keys and foreign key restore without stringified fetches #532

Merged

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Fix temporary table lookup without stringified fetches and with a different case - #522

Fix temporary table lookup without stringified fetches and with a different case#522
JanJakes merged 3 commits into
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Nandan108:fix/temporary-table-exists-lookup

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