System Catalogs
AionDB implements PostgreSQL-facing catalog and information schema views for compatibility with clients, drivers, and introspection queries.
information_schema
The v0.1 surface covers the standard schema-introspection tables most drivers and ORMs depend on. Every name below is a virtual relation served by the planner:
| Group | Tables |
|---|---|
| Schema overview | schemata, tables, views, columns, sequences, triggers, domains, routines, parameters |
| Constraints | table_constraints, key_column_usage, referential_constraints, constraint_column_usage |
| Privileges | table_privileges, role_table_grants, usage_privileges, role_usage_grants, applicable_roles, enabled_roles |
| Locale | character_sets, collations |
| Foreign data | foreign_data_wrappers, foreign_data_wrapper_options, foreign_servers, foreign_server_options, user_mappings, user_mapping_options, foreign_tables, foreign_table_options |
Example:
SELECT table_schema, table_name
FROM information_schema.tables
ORDER BY table_schema, table_name;Column introspection:
SELECT table_name, column_name, data_type
FROM information_schema.columns
WHERE table_schema = 'public'
ORDER BY table_name, ordinal_position;information_schema is the safer first target for generic tools because it is standardized and usually less tied to PostgreSQL internals than pg_catalog.
pg_catalog
AionDB includes virtual pg_catalog tables used by PostgreSQL drivers and ORMs. The current planner-served set is large enough to absorb common driver introspection paths without falling through to the general binder:
| Group | Tables |
|---|---|
| Schema graph | pg_namespace, pg_class, pg_attribute, pg_attrdef, pg_type, pg_range, pg_enum, pg_proc, pg_aggregate, pg_operator, pg_opclass, pg_opfamily, pg_amop, pg_amproc, pg_am, pg_cast, pg_conversion, pg_collation, pg_language, pg_tablespace, pg_database |
| Constraints & indexes | pg_index, pg_indexes, pg_constraint, pg_inherits, pg_partitioned_table |
| Views, sequences, matviews | pg_views, pg_tables, pg_sequence, pg_sequences, pg_matviews |
| Roles & ACLs | pg_authid, pg_roles, pg_user, pg_shadow, pg_auth_members, pg_init_privs, pg_default_acl, pg_policy |
| Statistics | pg_statistic, pg_statistic_ext, pg_statistic_ext_data, pg_stats, pg_stats_ext, pg_stats_ext_exprs |
| Runtime activity | pg_stat_activity, pg_stat_database, pg_stat_bgwriter, pg_stat_archiver, pg_stat_io, pg_stat_slru, pg_stat_wal, pg_stat_wal_receiver, pg_locks, pg_prepared_statements, pg_prepared_xacts, pg_stat_statements, pg_cursors, pg_backend_memory_contexts, pg_shmem_allocations |
| Per-relation stats | pg_stat_all_tables, pg_stat_user_tables, pg_statio_all_tables, pg_statio_user_tables, pg_stat_user_indexes, pg_statio_user_indexes, pg_stat_user_functions |
| Replication | pg_replication_slots, pg_replication_origin, pg_stat_replication, pg_publication, pg_publication_namespace, pg_publication_rel, pg_subscription |
| Settings & config | pg_settings, pg_config, pg_file_settings, pg_hba_file_rules, pg_ident_file_mappings, pg_db_role_setting |
| Extensions | pg_extension, pg_available_extensions, pg_available_extension_versions, pg_event_trigger, pg_trigger, pg_rewrite, pg_rules |
| Foreign data | pg_foreign_server, pg_foreign_table, pg_foreign_data_wrapper, pg_user_mapping, pg_user_mappings |
| Comments & labels | pg_description, pg_shdescription, pg_seclabel, pg_depend, pg_shdepend, pg_compat_object_attrs, pg_compat_trigger_state |
| Timezones | pg_timezone_abbrevs, pg_timezone_names |
| Full-text search | pg_ts_config, pg_ts_dict, pg_ts_parser, pg_ts_template |
| Large objects | pg_largeobject, pg_largeobject_metadata |
Example:
SELECT typname, oid
FROM pg_catalog.pg_type
ORDER BY oid
LIMIT 10;pg_catalog compatibility is harder because many tools depend on PostgreSQL-specific OIDs, type names, relation metadata, function rows, and constraint details. AionDB implements compatibility where needed, but v0.1 should not be treated as a full PostgreSQL catalog clone.
ORM introspection
ORMs often inspect:
- table names;
- column names and types;
- primary keys;
- indexes;
- constraints;
- sequences;
- server version;
- supported functions.
When an ORM fails before running application SQL, capture the catalog query it executed. That query belongs in the compatibility suite.
Example schema inspection
CREATE TABLE catalog_demo (
id INT PRIMARY KEY,
body TEXT
);
SELECT column_name, data_type
FROM information_schema.columns
WHERE table_name = 'catalog_demo'
ORDER BY ordinal_position;This is a useful smoke test because many drivers do the same kind of lookup automatically.
Compatibility posture
These catalogs exist for compatibility, but they are not a full PostgreSQL catalog implementation. Some client introspection queries are supported directly; others may fall back to the general planner or fail if they rely on unsupported PostgreSQL details.
When adding ORM support, capture the exact catalog query generated by the tool.
Reporting catalog gaps
Include:
- the client or ORM name and version;
- the catalog query;
- PostgreSQL output if used as reference;
- AionDB output or SQLSTATE;
- whether the query is required for connection, migration, or runtime behavior.