fix: order modified foreign keys after added unique constraints

[meesvandongen]

When a migration adds a new UNIQUE/PRIMARY KEY constraint and also modifies an existing foreign key to reference it, the foreign key can be recreated before the referenced constraint exists.

This change updates modified-table dependency ordering so modified foreign keys are applied after newly added referenced UNIQUE/PRIMARY KEY constraints.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds regression coverage and updates dependency ordering to ensure tables that add UNIQUE/PK constraints are processed before tables whose modified foreign keys reference them.

Changes:

• Extend topologicallySortModifiedTables to treat modified FKs as dependencies on newly added UNIQUE/PK constraints.
• Add a unit test covering “modified FK depends on added UNIQUE” ordering.
• Add new testdata fixtures (old/new schema + diff/plan outputs) for two related dependency scenarios.

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
testdata/diff/dependency/issue_modified_fk_to_new_unique_reverse_order/plan.txt	Adds expected human-readable plan output fixture for reverse-order scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique_reverse_order/plan.sql	Adds expected SQL plan fixture for reverse-order scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique_reverse_order/plan.json	Adds expected JSON plan fixture for reverse-order scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique_reverse_order/old.sql	Adds “before” schema fixture for reverse-order scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique_reverse_order/new.sql	Adds “after” schema fixture for reverse-order scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique_reverse_order/diff.sql	Adds expected diff SQL fixture for reverse-order scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique/plan.txt	Adds expected human-readable plan output fixture for non-prefixed tables scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique/plan.sql	Adds expected SQL plan fixture for non-prefixed tables scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique/plan.json	Adds expected JSON plan fixture for non-prefixed tables scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique/old.sql	Adds “before” schema fixture for non-prefixed tables scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique/new.sql	Adds “after” schema fixture for non-prefixed tables scenario.
testdata/diff/dependency/issue_modified_fk_to_new_unique/diff.sql	Adds expected diff SQL fixture for non-prefixed tables scenario.
internal/diff/topological_test.go	Adds regression test for ordering modified FK table after referenced table with newly added UNIQUE.
internal/diff/topological.go	Updates modified-table topological sort to consider dependencies from modified foreign keys.

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[greptile-apps]

Greptile Summary

This PR updates modified-table dependency ordering for foreign keys that target newly added keys. The main changes are:

• Modified foreign keys now participate in table ordering dependencies.
• Added UNIQUE and PRIMARY KEY constraints are ordered before dependent modified FKs.
• New regression fixtures cover same-order composite FK updates in normal and reverse table-name order.

Confidence Score: 3/5

This is close, but the ordering fix still misses a valid composite foreign key case.

• Same-order FK references are now handled.

• Reverse-order composite references can still skip the dependency edge.

• That can leave the migration ordering failure in place for valid PostgreSQL schemas.

• internal/diff/topological.go should match FK referenced columns using the same column-set semantics as the existing FK recreation planner.

Important Files Changed

Filename	Overview
internal/diff/topological.go	Extends modified-table ordering to inspect modified foreign key definitions.
internal/diff/topological_test.go	Adds unit coverage for a modified FK referencing a newly added UNIQUE constraint.

_{Reviews (1): Last reviewed commit: "fix: order modified foreign keys after a..." | Re-trigger Greptile}

[greptile-apps]

Match referenced column sets

This still only adds the dependency edge when the referenced column order exactly matches the new UNIQUE/PK order. PostgreSQL allows a composite FK such as REFERENCES parent (b, a) to use UNIQUE (a, b), and the existing FK recreation planner already treats this as an unordered column set. When a modified FK references the newly added key in the opposite order, constraintMatchesFKReference returns false, so the dependent table can still be ordered before the referenced table and the migration can fail before the unique constraint exists.

Suggested change

	if constraintMatchesFKReference(constraint, fkConstraint) {
	// Add edge: tableB (with new UNIQUE/PK) -> tableA (with new FK)
	adjList[keyB] = append(adjList[keyB], keyA)
	inDegree[keyA]++
	break
	return
	}
	if fkReferencesAnyConstraint(fkConstraint, []*ir.Constraint{constraint}) {
	adjList[keyB] = append(adjList[keyB], keyA)
	inDegree[keyA]++
	return
	}