fix: materialized view drop order that depends on table

[tianzhou]

Fix #185

[Copilot]

Pull request overview

This PR fixes the ordering of materialized view drops when those views depend on tables being modified or dropped. The fix ensures that materialized views are dropped before their dependent tables are altered, preventing PostgreSQL dependency errors.

Key changes:

• Added pre-drop phase for materialized views that depend on affected tables
• Modified the migration SQL generation flow to handle pre-dropped views
• Introduced viewDependsOnTable function to detect table dependencies in view definitions

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/diff/diff.go	Implements pre-drop logic for materialized views and updates migration generation flow to track pre-dropped views
internal/diff/view.go	Updates generateModifyViewsSQL to skip DROP for pre-dropped views and adds viewDependsOnTable helper function
testdata/diff/dependency/table_to_view/plan.txt	Test data showing expected plan output for table-to-view dependency scenario
testdata/diff/dependency/table_to_view/plan.sql	Test data with expected SQL for table-to-view dependency scenario
testdata/diff/dependency/table_to_view/plan.json	Test data with JSON plan for table-to-view dependency scenario
testdata/diff/dependency/table_to_view/old.sql	Test data with old schema state for table-to-view scenario
testdata/diff/dependency/table_to_view/new.sql	Test data with new schema state for table-to-view scenario
testdata/diff/dependency/table_to_view/diff.sql	Test data with expected diff SQL for table-to-view scenario
testdata/diff/dependency/table_to_materialized_view/plan.txt	Test data showing expected plan output with pre-drop of materialized view
testdata/diff/dependency/table_to_materialized_view/plan.sql	Test data with expected SQL showing DROP before ALTER TABLE
testdata/diff/dependency/table_to_materialized_view/plan.json	Test data with JSON plan showing proper operation ordering
testdata/diff/dependency/table_to_materialized_view/old.sql	Test data with old schema state including materialized view
testdata/diff/dependency/table_to_materialized_view/new.sql	Test data with new schema state with modified table and view
testdata/diff/dependency/table_to_materialized_view/diff.sql	Test data with expected diff SQL showing proper drop order

---

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

[Copilot]

The strings.Contains check for unqualified table names can produce false positives. For example, if tableName is "product", it will incorrectly match "products" or "product_items" in the view definition. Consider using word boundary matching (e.g., with regex \b) or a more sophisticated SQL parsing approach to avoid matching partial table names.

[Copilot]

The view key is constructed using diff.New.Schema + "." + diff.New.Name, but in generatePreDropMaterializedViewsSQL (line 952 of diff.go), the key is constructed using viewDiff.Old.Schema + "." + viewDiff.Old.Name. This inconsistency could cause the pre-dropped view check to fail if the view is renamed or moved to a different schema. Consider using the Old view's schema and name for both key construction and lookup to ensure consistency.

Suggested change

	viewKey := diff.New.Schema + "." + diff.New.Name
	viewKey := diff.Old.Schema + "." + diff.Old.Name