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Pg-Meta Composite Foreign Key Introspection Returns Cartesian Product Of Columns

pg-meta incorrectly introspects composite foreign keys by combining every source column with every target column instead of pairing them by ordinal position, leading to phantom relationships in metadata consumers.

highConfidence 95%Supabase/pg-Meta

Origin Analysis

The relationship introspection query joins source and target attributes using ANY(conkey) and ANY(confkey) independently without matching the array indices of pg_constraint.conkey and pg_constraint.confkey, causing PostgreSQL to produce a Cartesian product for composite foreign keys.

1. Create tables with a composite foreign key:\n```sql\nCREATE TABLE public.ctgt (x INT, y INT, PRIMARY KEY (x, y));\nCREATE TABLE public.csrc (a INT, b INT, FOREIGN KEY (a, b) REFERENCES public.ctgt (x, y));\n```\n2. Retrieve table metadata using pg-meta:\n```ts\nconst table = await pgMeta.tables.retrieve({ schema: "public", name: "csrc" });\nconsole.log(table.relationships);\n```\n3. Observe that the output contains four relationships (a->x, a->y, b->x, b->y) instead of the expected two (a->x, b->y).

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

This fix assumes the PostgreSQL version supports multi-array unnest with WITH ORDINALITY (available since 9.4). For older versions, a custom function using generate_subscripts would be required. Additionally, if conkey or confkey contain NULL or mismatched lengths (which should not happen for valid foreign keys), the unnest might produce unexpected rows; ensure constraints are valid before running. Rollback: if any regression occurs, revert to the original ANY() query, but note that the original query only manifests the bug for composite keys and does not cause crashes.