Schema retrieval and documentation

SELECT
  c.table_schema,
  c.table_name,
  c.ordinal_position,
  c.column_name,
  c.data_type,
  c.udt_name,
  c.is_nullable,
  c.column_default
FROM information_schema.columns AS c
WHERE c.table_schema = ANY($1::text[])
ORDER BY c.table_schema, c.table_name, c.ordinal_position;

SELECT
  n.nspname AS schema_name,
  cls.relname AS table_name,
  a.attname AS column_name,
  col_description(cls.oid, a.attnum) AS comment
FROM pg_catalog.pg_attribute AS a
JOIN pg_catalog.pg_class AS cls ON cls.oid = a.attrelid
JOIN pg_catalog.pg_namespace AS n ON n.oid = cls.relnamespace
WHERE n.nspname = ANY($1::text[])
  AND cls.relkind IN ('r', 'p')
  AND a.attnum > 0
  AND NOT a.attisdropped;

SELECT
  src_ns.nspname AS table_schema,
  src.relname AS table_name,
  src_col.attname AS column_name,
  dst_ns.nspname AS foreign_table_schema,
  dst.relname AS foreign_table_name,
  dst_col.attname AS foreign_column_name
FROM pg_catalog.pg_constraint AS con
JOIN pg_catalog.pg_class AS src ON src.oid = con.conrelid
JOIN pg_catalog.pg_namespace AS src_ns ON src_ns.oid = src.relnamespace
JOIN pg_catalog.pg_class AS dst ON dst.oid = con.confrelid
JOIN pg_catalog.pg_namespace AS dst_ns ON dst_ns.oid = dst.relnamespace
CROSS JOIN LATERAL unnest(con.conkey, con.confkey)
  AS key_columns(src_attnum, dst_attnum)
JOIN pg_catalog.pg_attribute AS src_col
  ON src_col.attrelid = src.oid AND src_col.attnum = key_columns.src_attnum
JOIN pg_catalog.pg_attribute AS dst_col
  ON dst_col.attrelid = dst.oid AND dst_col.attnum = key_columns.dst_attnum
WHERE con.contype = 'f'
  AND src_ns.nspname = ANY($1::text[])
ORDER BY con.oid, src_col.attnum;

merge migration
 → apply all migrations to an ephemeral database
 → extract catalogs
 → normalize ordering and remove environment values
 → generate JSON plus Markdown summaries
 → hash / bind migration version
 → review schema diff
 → publish to retrieval index