8f8f09008a
Track .cursor/rules/ in git so coding conventions are shared across the team. Everything else under .cursor/ stays ignored. Signed-off-by: Émile Ré <emile@probo.com>
53 lines
1.4 KiB
Plaintext
53 lines
1.4 KiB
Plaintext
---
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description: Upsert must RETURNING full row into pointer receiver, not use xmax
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globs: "pkg/coredata/**/*.go"
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alwaysApply: false
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---
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# Upsert: RETURNING full row into receiver
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Upsert methods use a **pointer receiver** and `RETURNING` all struct columns to sync the receiver with the actual DB state. Save the original ID before the query; compare it with the returned ID to detect insert vs update.
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Do **not** use `RETURNING (xmax = 0) AS inserted` — `xmax` is a PostgreSQL internal system column and is fragile.
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```go
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// GOOD — RETURNING full row, sync receiver
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func (t *Thing) Upsert(ctx context.Context, conn pg.Tx) (inserted bool, err error) {
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q := `
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INSERT INTO things (id, name, created_at, updated_at)
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VALUES (@id, @name, @created_at, @updated_at)
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ON CONFLICT (name) DO UPDATE
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SET
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name = EXCLUDED.name,
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updated_at = EXCLUDED.updated_at
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RETURNING
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id,
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name,
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created_at,
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updated_at
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`
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originalID := t.ID
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// ...args...
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rows, err := conn.Query(ctx, q, args)
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if err != nil {
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return false, fmt.Errorf("cannot upsert thing: %w", err)
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}
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defer rows.Close()
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row, err := pgx.CollectExactlyOneRow(rows, pgx.RowToStructByName[Thing])
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if err != nil {
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return false, fmt.Errorf("cannot collect upsert result: %w", err)
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}
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*t = row
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return originalID == t.ID, nil
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}
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// BAD — xmax trick
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RETURNING (xmax = 0) AS inserted
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// BAD — RETURNING only id without syncing receiver
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RETURNING id
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```
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