Phase 2.4: Partition table introspection

[aesslinger]

Part of the Phase 2 set of PostgreSQL-specific features beyond the built-in driver.

Problem

Declarative partitioned tables (PARTITION BY RANGE/LIST/HASH) are common in production PostgreSQL schemas, but Tabularis currently shows a partitioned table's children as unrelated, disconnected entries in the table list — there's no indication of the parent/child relationship, partition key, or bounds.

Proposed approach

-- Find partitioned tables
SELECT c.relname, pg_get_partkeydef(c.oid) as partition_key
FROM pg_class c
JOIN pg_namespace n ON c.relnamespace = n.oid
WHERE c.relkind = 'p' AND n.nspname = $1;

-- Find partitions of a parent table
SELECT c.relname, pg_get_expr(c.relpartbound, c.oid) as partition_bound
FROM pg_inherits i
JOIN pg_class c ON i.inhrelid = c.oid
WHERE i.inhparent = (SELECT oid FROM pg_class WHERE relname = $1);

Frontend integration

• Partitioned tables show with a distinct icon in the sidebar.
• Expanding a partitioned table shows its child partitions with their bounds.
• Context menu adds "Create Partition" / "Detach Partition" actions.

Acceptance criteria

• Partitioned tables are visually distinguishable from regular tables in the sidebar
• Expanding a partitioned table lists its children with correct partition bounds
• Both range and list partitioning display correctly (hash partitioning bounds may need separate handling — verify)
• No regressions in existing Phase 1 parity tests

Tests

• test_get_partitioned_tables — identifies partition parents
• test_get_partitions — lists children with bounds
• test_partition_range_bounds — range partition display
• test_partition_list_bounds — list partition display

References

• Full spec: docs/planning/03-phase-2-issue-16.md (2.4)
• Priority: Sprint 4 — medium demand