[Nandan108]

Summary

Follow-up to #523.

When a foreign key references columns with a different letter case than the referenced table declares them, the referenced unique constraint is not found:

CREATE TABLE t1 (id INT, name VARCHAR(255), PRIMARY KEY (id, name));
CREATE TABLE t2 (id INT, name VARCHAR(255), FOREIGN KEY (id, name) REFERENCES t1 (ID, Name));
SELECT unique_constraint_name FROM information_schema.referential_constraints WHERE table_name = 't2';
-- NULL   (MySQL: PRIMARY)

MySQL column names are case-insensitive, but the lookup compared the referenced column names to the index columns with !==. The foreign key itself works, since SQLite also matches column names case-insensitively; only the information schema entry is wrong.

Fix

The names are compared case-insensitively with strcasecmp(), which compares them directly, without creating lowercased copies first. Identifiers are restricted to ASCII in this driver, so this is sufficient.

Tests

testInformationSchemaForeignKeysReferencingColumnsInDifferentLetterCase references a single-column primary key, a composite unique key, and a unique key in a foreign key added with ALTER TABLE, all with differently cased column names, and checks UNIQUE_CONSTRAINT_NAME. It fails on trunk with NULL for all three.

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
  • Foreign-key metadata now correctly matches referenced columns when their names use different letter casing. This applies to single-column and composite references, whether constraints are defined during table creation or added afterward.
  • Information schema results now identify the expected unique indexes for these foreign-key references, including primary-key references.

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Reviewing files that changed from the base of the PR and between 81d6afa and bffd503.

📒 Files selected for processing: 2

• packages/mysql-on-sqlite/src/sqlite/class-wp-sqlite-information-schema-builder.php
• packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Metadata_Tests.php

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📝 Walkthrough

The information-schema builder now matches referenced foreign-key columns without regard to letter case. A metadata test covers references to primary and composite unique keys, including an added constraint.

Changes: Foreign-key metadata matching

Layer / File(s)	Summary
Match referenced columns and validate metadata packages/mysql-on-sqlite/src/sqlite/class-wp-sqlite-information-schema-builder.php, packages/mysql-on-sqlite/tests/WP_MySQL_On_SQLite_Metadata_Tests.php	The builder uses case-insensitive comparison when matching referenced columns to unique-index prefixes. The test checks metadata for primary-key, composite unique-key, and added-constraint references with different letter casing.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Bug fix

Suggested reviewers: janjakes

Merge Risk: ⚪ Minimal · up to bffd5

The foreign-key metadata change appears ready to merge after normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 2 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 and concisely describes the main change: fixing case-sensitive matching between foreign key references and unique keys.

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[JanJakes]

Thanks again, @Nandan108! I rebased the branch on the latest trunk and pushed one commit on top with small improvements (strcasecmp() to avoid string allocation, improved test coverage).