fix: always schema-qualify table in COMMENT ON COLUMN (#502)

[tianzhou]

Summary

• Always schema-qualify the table name in COMMENT ON COLUMN emissions so that stripSchemaQualifications can safely strip the schema prefix without mangling the table.column reference
• Fixes the case where a table name matches the target schema name (e.g., table public in schema public), which caused stripSchemaQualifications to strip the table qualifier producing invalid SQL
• Updated 3 COMMENT ON COLUMN emission sites in internal/diff/table.go and all golden test files

Test plan

• Added comment/issue_502_column_comment_table_name_matches_schema test fixture with table named public in schema public
• All existing comment diff tests pass (golden files updated with public. prefix)
• All plan-and-apply comment tests pass
• Full test suite passes

Closes #502

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

This PR fixes a bug where stripSchemaQualifications would incorrectly strip the table qualifier from COMMENT ON COLUMN SQL when the table name matches the target schema name (e.g., a table named public in schema public). The fix is to always schema-qualify the table name in all three COMMENT ON COLUMN emission sites, so the output is always schema.table.column, giving stripSchemaQualifications an unambiguous schema prefix to strip.

• All three COMMENT ON COLUMN emission sites in internal/diff/table.go now unconditionally use ir.QuoteIdentifier(schema).ir.QuoteIdentifier(table) instead of the conditional qualifyEntityNameMode/getTableNameWithSchema helpers that omit the schema prefix when schema equals targetSchema.
• A new golden test fixture (issue_502_column_comment_table_name_matches_schema) validates the specific failure case, and all existing golden files are updated to reflect the new schema.table.column format.

Confidence Score: 5/5

The change is safe to merge — it correctly fixes a narrow SQL-generation bug without any collateral risk to the broader diff or plan pipeline.

All three COMMENT ON COLUMN emission sites are updated consistently. The fix is logically sound: always emitting schema.table lets stripSchemaQualifications strip exactly one prefix level, regardless of whether the table name coincidentally matches the schema name. The golden test files are fully updated and a dedicated regression fixture is added. No other code paths are affected.

No files require special attention.

Important Files Changed

Filename	Overview
internal/diff/table.go	Three COMMENT ON COLUMN emission sites updated to always schema-qualify the table name; COMMENT ON TABLE is intentionally unchanged (2-part name has no ambiguity).
testdata/diff/comment/issue_502_column_comment_table_name_matches_schema/new.sql	New test fixture reproducing the bug: table named public in schema public, correctly verifies public.public.column output.
testdata/diff/comment/add_column_comments/diff.sql	Golden file updated to reflect always-schema-qualified COMMENT ON COLUMN output (public.products.id, etc.).
testdata/diff/comment/mixed_comments/diff.sql	Golden file updated consistently with the new schema-qualified column comment format.
testdata/diff/create_table/add_table_like/diff.sql	Golden file updated to include schema prefix on COMMENT ON COLUMN for the table-like test case.

_{Reviews (1): Last reviewed commit: "fix: always schema-qualify table in COMM..." | Re-trigger Greptile}

[Copilot]

Pull request overview

This PR fixes a dump→plan round-trip failure for COMMENT ON COLUMN when a table name matches the target schema name (Issue #502) by ensuring COMMENT ON COLUMN statements are emitted with a schema-qualified table reference (i.e., schema.table.column), allowing stripSchemaQualifications to remove only the schema prefix without misinterpreting table.column as schema.object.

Changes:

• Always emit COMMENT ON COLUMN using schema.table.column in internal/diff/table.go (create tables, added columns, modified column comments).
• Add a regression fixture covering the “table name equals schema name” case.
• Update existing golden outputs to reflect the new public.-qualified COMMENT ON COLUMN SQL.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/diff/table.go	Emits schema-qualified table names for COMMENT ON COLUMN to prevent stripSchemaQualifications from stripping the wrong qualifier.
testdata/diff/create_table/add_table_like/plan.txt	Updates golden plan output to include public. qualification for column comments.
testdata/diff/create_table/add_table_like/plan.sql	Updates golden SQL output to include public. qualification for column comments.
testdata/diff/create_table/add_table_like/plan.json	Updates golden JSON output to include public. qualification for column comments.
testdata/diff/create_table/add_table_like/diff.sql	Updates golden diff output to include public. qualification for column comments.
testdata/diff/comment/mixed_comments/plan.txt	Updates golden plan output to include public. qualification for column comments.
testdata/diff/comment/mixed_comments/plan.sql	Updates golden SQL output to include public. qualification for column comments.
testdata/diff/comment/mixed_comments/plan.json	Updates golden JSON output to include public. qualification for column comments.
testdata/diff/comment/mixed_comments/diff.sql	Updates golden diff output to include public. qualification for column comments.
testdata/diff/comment/issue_502_column_comment_table_name_matches_schema/plan.txt	Adds regression fixture demonstrating correct handling when table name matches schema name.
testdata/diff/comment/issue_502_column_comment_table_name_matches_schema/plan.sql	Adds regression fixture SQL output for the new edge case.
testdata/diff/comment/issue_502_column_comment_table_name_matches_schema/plan.json	Adds regression fixture JSON output for the new edge case.
testdata/diff/comment/issue_502_column_comment_table_name_matches_schema/old.sql	Adds old-state SQL for the regression fixture.
testdata/diff/comment/issue_502_column_comment_table_name_matches_schema/new.sql	Adds new-state SQL (with column comments) for the regression fixture.
testdata/diff/comment/issue_502_column_comment_table_name_matches_schema/diff.sql	Adds expected diff SQL for the regression fixture.
testdata/diff/comment/column_comment_quoted_identifier/plan.txt	Updates golden output to include public. qualification for quoted-column comment case.
testdata/diff/comment/column_comment_quoted_identifier/plan.sql	Updates golden SQL output to include public. qualification for quoted-column comment case.
testdata/diff/comment/column_comment_quoted_identifier/plan.json	Updates golden JSON output to include public. qualification for quoted-column comment case.
testdata/diff/comment/column_comment_quoted_identifier/diff.sql	Updates golden diff output to include public. qualification for quoted-column comment case.
testdata/diff/comment/add_column_comments/plan.txt	Updates golden plan output to include public. qualification for column comments.
testdata/diff/comment/add_column_comments/plan.sql	Updates golden SQL output to include public. qualification for column comments.
testdata/diff/comment/add_column_comments/plan.json	Updates golden JSON output to include public. qualification for column comments.
testdata/diff/comment/add_column_comments/diff.sql	Updates golden diff output to include public. qualification for column comments.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.