fix(drizzle-kit): handle MySQL functional/expression indexes in introspection

[cyphercodes]

Bug Description

MySQL 8+ functional indexes have COLUMN_NAME = null in INFORMATION_SCHEMA.STATISTICS with the actual expression stored in the EXPRESSION column. This caused drizzle-kit pull to crash with:

TypeError: Cannot read properties of null (reading 'camelCase')

when introspecting databases with functional/expression indexes.

Changes

mysqlSerializer.ts

• Check for null COLUMN_NAME and use EXPRESSION column instead for functional indexes
• Track expression columns in internals.indexes for proper TypeScript generation
• Skip entries where both COLUMN_NAME and EXPRESSION are null

introspect-mysql.ts

• Updated createTableIndexes and createTableUniques to accept schema parameter
• Expression columns are now wrapped in sql\...`instead oftable.column`

Example

Before (crash):

CREATE UNIQUE INDEX idx ON table ((CASE WHEN col = 1 THEN 1 ELSE NULL END));

After (works):

unique("idx").on(sql`CASE WHEN col = 1 THEN 1 ELSE NULL END`)

Testing

This fix was tested against the reproduction case provided in #5546.

Fixes #5546