fix: index operators

[tianzhou]

Fix #132

[Copilot]

Pull Request Overview

This pull request adds support for extracting and generating PostgreSQL index operator classes (e.g., varchar_pattern_ops) in index definitions. The changes enable the schema diffing tool to properly handle indexes that use non-default operator classes.

Key changes:

• Enhanced database queries to extract operator class information from PostgreSQL system catalogs
• Updated the index building logic to populate operator class data in the IR
• Modified index SQL generation to include operator class specifications

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
testdata/diff/create_index/add_index/*.sql	Test cases demonstrating index creation with operator classes (varchar_pattern_ops)
testdata/diff/create_index/add_index/*.json	JSON plan output showing operator class in migration steps
ir/queries/queries.sql	Added SQL query to extract operator class names from pg_opclass catalog
ir/queries/queries.sql.go	Generated code reflecting new column_opclasses field and removed unused function parameter fields
ir/inspector.go	Updated index building to populate operator class from query results; added unused parseIndexColumnDefinition function
internal/diff/index.go	Modified index SQL generation to include operator class in CREATE INDEX statements

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.