pg_dump

Development

Consult PostgreSQL's pg_dump implementation for guidance on system catalog queries and schema extraction when implementing pgschema features. Use this skill when adding new schema object support, debugging inspector.go queries, understanding how PostgreSQL represents objects internally, or handling version-specific features across PostgreSQL 14-18.

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pg_dump Reference

Reference pg_dump's implementation for correct system catalog queries and schema extraction patterns.

Source

Repository: https://github.com/postgres/postgres/blob/master/src/bin/pg_dump/

Key files:

pg_dump.c - Main implementation with all system catalog queries
pg_dump.h - Data structures
pg_dump_sort.c - Dependency sorting
common.c - Shared catalog query utilities

Object Type → pg_dump Function → System Catalogs

Object	Function	Catalogs
Tables & Columns	`getTables()`	`pg_class`, `pg_attribute`, `pg_type`
Constraints	`getConstraints()`	`pg_constraint`
Indexes	`getIndexes()`	`pg_index`, `pg_class`
Triggers	`getTriggers()`	`pg_trigger`, `pg_proc`
Functions	`getFuncs()`	`pg_proc`
Views	`getViews()`	`pg_class`, `pg_rewrite`
Sequences	`getSequences()`	`pg_sequence`, `pg_class`
Policies	`getPolicies()`	`pg_policy`
Types	`getTypes()`	`pg_type`
Aggregates	`getAggregates()`	`pg_aggregate`, `pg_proc`
Comments	`getComments()`	`pg_description`

Key Helper Functions

pg_get_expr(expr, relation, pretty) - Deparse expressions (defaults, WHEN clauses, index predicates)
pg_get_constraintdef(oid, pretty) - Get constraint DDL
pg_get_indexdef(oid, column, pretty) - Get index DDL
pg_get_triggerdef(oid, pretty) - Get full trigger DDL

Important: For trigger WHEN clauses, always use pg_get_expr(t.tgqual, t.tgrelid, false) from pg_catalog.pg_trigger. Do NOT use information_schema.triggers.action_condition.

Workflow

Identify the object type you're implementing
Find the pg_dump function from the table above
Read the system catalog query — note which columns, joins, and helper functions are used
Check version-specific handling — pg_dump uses fout->remoteVersion checks
Adapt for pgschema in ir/inspector.go or ir/queries/:
- Use pgx parameter binding
- Handle NULLs appropriately
- Add version detection if needed

When pg_dump is Authoritative

Always reference for: system catalog query patterns, correct use of pg_get_* functions, version-specific feature detection, object dependency tracking.

When NOT to Copy pg_dump

Don't copy: output formatting (pgschema has different conventions), archive/restore logic, full-database scope (pgschema is schema-focused), pre-PG14 compatibility.

pgschema Adaptation Pattern

// pg_dump query pattern:
// SELECT t.tgname, pg_get_expr(t.tgqual, t.tgrelid, false) as when_clause
// FROM pg_catalog.pg_trigger t WHERE ...

// pgschema adaptation (in ir/inspector.go or ir/queries/):
query := `SELECT t.tgname, pg_get_expr(t.tgqual, t.tgrelid, false)
FROM pg_catalog.pg_trigger t
WHERE t.tgrelid = $1 AND NOT t.tgisinternal`
rows, err := conn.Query(ctx, query, tableOID)