fix schema.c: filter out internal partition FK clones when listing FK constraints#41
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pgcopydb lists FK constraints straight from pg_constraint and creates them
directly. On a partitioned schema that also returns Postgres's internal
per-partition FK clones (pg_constraint.conparentid <> 0): once the top-level
constraint is created it cascades to every partition, then pgcopydb tries to
create each clone again and hits "constraint already exists" — one ERROR per
clone, so a migration that actually succeeds looks like it failed.
Filter the clones out with c.conparentid = 0; recreating the top-level
constraint re-cascades to all partitions, so nothing is lost (mirrors
pg_dump). It cannot be a static SQL constant, though:
- conparentid is PG 11+ only; referencing it on a 9.x/10 source aborts the
clone with "column c.conparentid does not exist". Those sources are still
supported (follow-9.6) and cannot have partition FK clones anyway.
- --defer-validate-fks relies on the clones: PG < 18 rejects NOT VALID on a
partitioned parent, so pgcopydb skips the parent and creates the per-leaf
clones NOT VALID instead, which is the only enforcement that lands.
So the predicate is injected at runtime in schema_list_fk_constraints only
when the source is PG >= 11 and --defer-validate-fks is off.
Adds a fk-partition-clone test (HASH-partitioned table with FKs to regular
tables) asserting the clone finishes with no "constraint already exists"
errors and correct, validated FKs on the target. Verified locally: full suite
green on PG16/PG18; FK and partition suites green on PG16/17/18.
teknogeek0
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Filter internal partition FK clones from FK constraint listing
Problem
FK_BASE_WHEREinschema.cfiltered FK constraints oncontype = 'f'with noconparentidguard, solistSourceFKConstraintsSQLreturned Postgres's internalper-partition FK clones (
conparentid != 0) alongside the real top-levelconstraints. On a partitioned schema this caused two failures:
clone's
pg_get_constraintdef()rendersREFERENCES <specific_partition>.Recreating all of them produces standalone single-partition FKs; since a key
lives in exactly one partition, no row can satisfy all of them at once, so the
first insert — and CDC apply — fails.
constraint already existserrors. Clones on a partitionedreferencing table are recreated automatically via
CASCADEwhen the parentFK is added, so explicitly listing them collided.
Fix
One line:
AND c.conparentid = 0inFK_BASE_WHERE(shared by all 5 filtervariants), so only top-level constraints are listed. This mirrors
pg_dump,which excludes cascade clones the same way. Recreating the parent constraint
re-cascades to all partitions, so no clone is lost.
#define FK_BASE_WHERE \ " WHERE c.contype = 'f' " \ + " AND c.conparentid = 0 " \ " AND n.nspname !~ '^pg_' " \