fix: emit per-child column overrides in PARTITION OF (#499)

[tianzhou]

Summary

• When a partition child overrides DEFAULT or NOT NULL relative to its parent, the PARTITION OF statement now includes the column-element list (e.g. priority DEFAULT 10, notes NOT NULL).
• Adds allTables map to generateTableSQL so it can compare child columns against the parent and detect overrides.
• Adds test case issue_499_partition_column_overrides with full diff/plan fixtures.

Closes #499

Test plan

• TestDiffFromFiles/create_table_issue_499_partition_column_overrides passes
• All internal/diff tests pass
• CI green

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR extends the CREATE TABLE ... PARTITION OF ... emission path so that partition children can include a typed-table element list when they override DEFAULT and/or NOT NULL relative to the parent, aligning generated DDL with PostgreSQL’s supported grammar and addressing issue #499.

Changes:

• Detect per-child column overrides for partition children and include them in the PARTITION OF (...) element list.
• Thread an allTables lookup into generateTableSQL to compare child columns against the parent.
• Add a new fixture-backed test case (issue_499_partition_column_overrides) validating the emitted plan/DDL.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/diff/table.go	Adds partition-child column override detection and includes override elements in the PARTITION OF (...) list.
internal/diff/qualify_schema_test.go	Updates test helper calls for the new generateTableSQL(..., allTables) signature.
testdata/diff/create_table/issue_499_partition_column_overrides/plan.txt	New expected plan output for the added fixture.
testdata/diff/create_table/issue_499_partition_column_overrides/plan.sql	New expected SQL plan output for the added fixture.
testdata/diff/create_table/issue_499_partition_column_overrides/plan.json	New expected JSON plan output for the added fixture.
testdata/diff/create_table/issue_499_partition_column_overrides/old.sql	New fixture: empty starting schema.
testdata/diff/create_table/issue_499_partition_column_overrides/new.sql	New fixture: partitioned table + child overrides.
testdata/diff/create_table/issue_499_partition_column_overrides/diff.sql	New expected diff SQL for the fixture.

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[greptile-apps]

Greptile Summary

This PR fixes issue #499 by emitting per-child column overrides (DEFAULT, NOT NULL) in PARTITION OF DDL when a partition child diverges from its parent. It introduces an allTables lookup map inside generateCreateTablesSQL and threads it through to generateTableSQL, where parent–child column comparisons drive the new override emission.

• internal/diff/table.go: builds an allTables map from the batch of tables being created and passes it to generateTableSQL; the function now compares each child column against its parent to detect DEFAULT and NOT NULL overrides and emits them in the PARTITION OF body.
• testdata/diff/create_table/issue_499_partition_column_overrides/: adds a complete fixture set (old/new SQL, diff, plan) covering a list-partitioned orders table with orders_us having priority DEFAULT 10 and notes NOT NULL overrides.

Confidence Score: 3/5

The fix correctly handles the tested scenario but silently produces wrong DDL in two real migration paths, making it unsafe to merge as-is.

The allTables map is scoped to each call of generateCreateTablesSQL. Because diff.go calls that function twice with two disjoint table batches, a child in batch 2 cannot see a parent from batch 1. Separately, when a partition child is added to a pre-existing parent, the parent is absent from addedTables entirely. In both cases the override detection guard silently falls through, emitting bare PARTITION OF DDL without column overrides — and since PostgreSQL has no ALTER path to add them post-creation, the resulting schema is permanently wrong without any error or warning.

internal/diff/table.go — specifically the allTables construction and the parentKey lookup inside generateTableSQL

Important Files Changed

Filename	Overview
internal/diff/table.go	Core change: builds allTables from the current batch and threads it into generateTableSQL for parent–child column override detection; has gaps when parent and child land in different creation batches or when the parent already exists.
internal/diff/qualify_schema_test.go	Trivially updated to pass nil as the new allTables argument; nil map reads are safe in Go.
testdata/diff/create_table/issue_499_partition_column_overrides/diff.sql	Expected migration DDL fixture; matches the override logic being tested (priority DEFAULT 10, notes NOT NULL on orders_us).
testdata/diff/create_table/issue_499_partition_column_overrides/new.sql	New schema fixture; correctly defines orders_us with priority DEFAULT 10 and notes NOT NULL overrides, and orders_eu with no overrides.
testdata/diff/create_table/issue_499_partition_column_overrides/plan.json	Plan JSON fixture; captures expected SQL for all three tables including the override in orders_us.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[generateCreateTablesSQL\ncalled with batch of new tables] --> B[Build allTables map\nfrom batch only]
    B --> C[For each table in batch]
    C --> D{table.PartitionOf != ''}
    D -- No --> E[Emit standard CREATE TABLE]
    D -- Yes --> F{parentKey in allTables?}
    F -- No --> G[No override detection\n⚠ silent miss if parent\nin different batch or\nalready exists]
    F -- Yes --> H[For each child column\ncompare with parent column]
    H --> I{childDefault != parentDefault\nAND child has DEFAULT?}
    I -- Yes --> J[Append DEFAULT override]
    I -- No --> K{child NOT NULL\nAND parent nullable?}
    J --> K
    K -- Yes --> L[Append NOT NULL override]
    K -- No --> M[Next column]
    L --> M
    M --> N{More columns?}
    N -- Yes --> H
    N -- No --> O[Combine elementParts + constraintParts]
    O --> P{Any parts?}
    P -- Yes --> Q[Emit PARTITION OF with column element list]
    P -- No --> R[Emit bare PARTITION OF]

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flowchart TD
    A[generateCreateTablesSQL\ncalled with batch of new tables] --> B[Build allTables map\nfrom batch only]
    B --> C[For each table in batch]
    C --> D{table.PartitionOf != ''}
    D -- No --> E[Emit standard CREATE TABLE]
    D -- Yes --> F{parentKey in allTables?}
    F -- No --> G[No override detection\n⚠ silent miss if parent\nin different batch or\nalready exists]
    F -- Yes --> H[For each child column\ncompare with parent column]
    H --> I{childDefault != parentDefault\nAND child has DEFAULT?}
    I -- Yes --> J[Append DEFAULT override]
    I -- No --> K{child NOT NULL\nAND parent nullable?}
    J --> K
    K -- Yes --> L[Append NOT NULL override]
    K -- No --> M[Next column]
    L --> M
    M --> N{More columns?}
    N -- Yes --> H
    N -- No --> O[Combine elementParts + constraintParts]
    O --> P{Any parts?}
    P -- Yes --> Q[Emit PARTITION OF with column element list]
    P -- No --> R[Emit bare PARTITION OF]

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_{Reviews (1): Last reviewed commit: "fix: emit per-child column overrides (DE..." | Re-trigger Greptile}

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

[tianzhou]

Re-checked the latest head after 7decbf3 and 0c77576.

The earlier blocker was real, but it is now addressed: parent lookup for partition-column override comparison is sourced from the full target IR, and the incremental existing-parent case is covered by the new regression fixture. The remaining CI failure was only the stale plan fixture hash, which 0c77576 corrected.

Current CI is green on the latest head. Greptile's remaining summary is stale and refers to the older d775dc1 snapshot. No remaining findings from the reviewer pass; ready to merge.