Multi-version Postgres support

pgRDF builds against PostgreSQL 14, 15, 16, and 17. The full test bar runs across all four in CI.

Supported versions

Postgres major	Status	Notes
14	✅ supported	Active in CI matrix.
15	✅ supported	Active in CI matrix.
16	✅ supported	Active in CI matrix.
17	✅ supported	Default in compose-up.
18	⏳ deferred	pgrx 0.18.0 upstream still fails to build locally; see ERRATA E-006. Will land when pgrx ships a working 0.18.x.

What's tested where

Layer	Versions covered
just test — pgrx integration	PG 14-17
just test-regression — compose	PG 17 (the default compose target)
just test-w3c — W3C SPARQL conformance	PG 17
just test-lubm	PG 17
just test-everything	full sweep

The release workflow ships per-PG binary tarballs:

pgrdf-<ver>-pg14-glibc-amd64.tar.gz
pgrdf-<ver>-pg14-glibc-arm64.tar.gz
pgrdf-<ver>-pg15-glibc-amd64.tar.gz
…

per SPEC.pgRDF.INSTALL.v0.2.

Which cargo pgrx feature to pass

pgrx uses per-PG features. When building or running tests locally, pick one explicitly:

cargo pgrx run pg17 --features pg17
cargo pgrx test pg16 --features pg16

There is no default feature — default = [] — to avoid the "build silently picked the wrong PG version" failure mode.