feat(catalog): virtual system catalog (information_schema + pg_catalog) - #31
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ORMs and SQL tools introspect the catalog on connect; this answers those
queries. Adds virtual system relations that generate rows from existing
catalog metadata at read time (no stored copy, always consistent):
- information_schema.{schemata, tables, columns}
- pg_catalog.{pg_database, pg_namespace, pg_class, pg_attribute, pg_type},
resolvable qualified or unqualified (search-path style)
- st_* canonical spellings (st_class, st_type, …) aliased to the same
generators
A type-OID table maps each LogicalType to its canonical Postgres type OID
(int4=23, text=25, numeric=1700, uuid=2950, …) — the same map the wire
RowDescription should eventually send.
Mechanism: a SystemRelation enum owns each relation's schema + row
generation; the binder intercepts system names (1/2/3-part) into a new
LogicalNode/PlanNode::SystemScan, which the Volcano executor fills by
enumerating projects/datasets/tables via CatalogReader. Reshaping blob
metadata into columnar catalog rows is why a dedicated node exists (vs a
plain SeqScan); a real VIEW system would subsume it later.
Covered by system_catalog.slt. Wire column *names* (RowDescription) are
still generic for all queries — a separate follow-up for full ORM use.
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Summary
Adds a virtual system catalog so ORMs and SQL tools that introspect on connect get answers. Rows are generated from existing catalog metadata at read time — no stored copy, always consistent.
information_schema.{schemata, tables, columns}pg_catalog.{pg_database, pg_namespace, pg_class, pg_attribute, pg_type}, resolvable qualified or unqualified (search-path style)st_*canonical spellings (st_class,st_type, …) aliased to the same generatorsLogicalTypeto its canonical Postgres type OID (int4=23, text=25, numeric=1700, uuid=2950, …)Mechanism
A
SystemRelationenum owns each relation's schema + row generation. The binder intercepts system names (1/2/3-part) into a newLogicalNode/PlanNode::SystemScan, which the Volcano executor fills by enumerating projects/datasets/tables viaCatalogReader.Testing
Covered by
system_catalog.slt. Wire column names (RowDescription) are still generic — a separate follow-up for full ORM use.🤖 Generated with Claude Code