fix: commit enum ADD VALUE before statements that use the new label (#600)

[tianzhou]

Summary

Adding an enum label and using it in the same plan (e.g. as a column default) produced a plan that failed on apply:

ERROR: unsafe use of new value "active" of enum type status (SQLSTATE 55P04)

PostgreSQL requires ALTER TYPE ... ADD VALUE to be committed before the new label can be used, but groupDiffs batched every non-rewrite statement into one transaction group.

Fix:

• Add SQLStatement.RequiresCommitAfter (not serialized) and set it for enum ADD VALUE statements.
• groupDiffs closes the current execution group right after such a statement. ADD VALUE still shares a transaction with the steps before it; everything after it starts a new group.

The plan now shows the boundary explicitly:

-- Transaction Group #1
ALTER TYPE status ADD VALUE 'archived' AFTER 'pending';

-- Transaction Group #2
ALTER TABLE work ALTER COLUMN state SET DEFAULT 'archived'::status;

Atomicity note: if a later group fails, the added label stays. That is harmless — re-planning sees the label as present and emits only the remaining steps.

Fixes #600

Test plan

Folded the scenario into testdata/diff/create_type/add_type (the existing enum ADD VALUE case): a table whose default switches to the newly added label. Failed with 55P04 before the fix, passes after.

PGSCHEMA_TEST_FILTER="create_type/" go test -v ./internal/diff -run TestDiffFromFiles
PGSCHEMA_TEST_FILTER="create_type/" go test -v ./cmd -run TestPlanAndApply
go test ./internal/plan

🤖 Generated with Claude Code

[greptile-apps]

Confidence Score: 4/5

The PR is not yet safe to merge because plans still fail when a newly created object uses a label being added to an existing enum.

Findings

1.  Enum consumers can run first ▶

Summary

This PR marks enum ADD VALUE statements as requiring a following transaction boundary and updates plan grouping so later statements execute after that transaction commits.

• Propagates commit-boundary metadata from enum diff generation into planning.
• Splits execution groups immediately after each enum-label addition.
• Adds a regression fixture for changing an existing table default to the new label.
• The fix remains incomplete for newly created objects that use the label because create operations are ordered before enum modifications.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Existing enum gains archived label]
    B[Create phase]
    C["CREATE TABLE work<br/>DEFAULT archived::status"]
    D[Modify phase]
    E["ALTER TYPE status<br/>ADD VALUE archived"]
    F[Commit boundary after ADD VALUE]
    G[Apply fails before reaching ADD VALUE]

    A --> B
    B --> C
    C --> G
    A --> D
    D --> E
    E --> F

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_{Reviews (1) · Last reviewed commit: "fix: commit enum ADD VALUE before statem..."}

[Copilot]

Copilot review overview

🟡 Changes recommended

Create-phase objects can still reference a new enum label before its addition is emitted.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Schedule enum additions before dependent CREATE TABLE statements · New

What changed in this PR

Adds a commit boundary after PostgreSQL enum values are added so later statements can safely use them.

Changes:

• Marks enum ADD VALUE statements as requiring a commit.
• Splits execution groups at the new boundary.
• Extends the enum fixture with a dependent column default.

File	Description
testdata/​diff/​create_type/​add_type/​plan.txt	Updates human-readable plan output.
testdata/​diff/​create_type/​add_type/​plan.sql	Adds the default alteration SQL.
testdata/​diff/​create_type/​add_type/​plan.json	Expects two execution groups.
testdata/​diff/​create_type/​add_type/​old.sql	Adds the existing test table.
testdata/​diff/​create_type/​add_type/​new.sql	Uses the new enum label as a default.
testdata/​diff/​create_type/​add_type/​diff.sql	Updates expected migration SQL.
internal/​plan/​plan.go	Closes groups after commit-required statements.
internal/​diff/​type.go	Marks enum additions as commit-required.
internal/​diff/​diff.go	Adds statement commit-boundary metadata.
internal/​diff/​collector.go	Propagates commit-boundary metadata.

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[Copilot]

Copilot review overview

🟡 Changes recommended

The current ordering can commit preceding destructive drops if a later migration group fails.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Emit enum additions before destructive pre-drop and drop operations · New

Resolved since last review (1)

• Schedule enum additions before dependent CREATE TABLE statements

[Copilot]

Copilot review overview

🟡 Changes recommended

Apply must retain one database session across execution groups so session-scoped settings remain effective.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Use one connection to preserve search_path across apply groups · New

Resolved since last review (1)

• Emit enum additions before destructive pre-drop and drop operations