System Catalog

Goal: Describe the structure and purpose of AngaraBase system tables for monitoring, diagnostics, and metadata management.

The AngaraBase system catalog is accessible via the sys virtual schema. These tables provide real-time information about the instance state, configuration, and database objects.

`sys.tables` Table

Contains metadata for all tables across all databases and schemas.

Field	Type	Description
`db_id`	`string`	Database identifier.
`schema_name`	`string`	Schema name (usually `public`).
`table_name`	`string`	Table name.
`tablespace_name`	`string`	Tablespace name.
`storage_engine`	`string`	Storage engine type: `row_store` (HeapFile), `memory` (In-memory), `htap_row_column`.
`durability`	`string`	Durability level (for memory tables): `none`, `logged`, `snapshotted`.
`max_rows`	`uint64`	Row limit (for memory tables).
`eviction_policy`	`string`	Eviction policy (for memory tables): `error`, `fifo`, `lru`, `lfu`.
`checkpoint_interval_ms`	`uint64`	Checkpoint interval in ms (for `snapshotted`).
`current_rows`	`uint64`	Current number of live rows (approximate).
`evictions_total`	`uint64`	Counter of evicted rows.
`limit_errors_total`	`uint64`	Counter of row limit exceeded errors.
`append_only`	`bool`	Append-only mode flag (deprecated, see `mutation_policy`).
`mutation_policy`	`string`	Mutation policy: `unrestricted`, `no_delete`, `append_only`.

Storage Engine Note

row_store: Standard disk storage (HeapFile).
memory: Data is stored in RAM. Durability is controlled by the durability parameter.

`sys.settings` Table

Provides access to the current server configuration settings (Effective Configuration).

Field	Type	Description
`name`	`string`	Parameter name (e.g., `server.addr`).
`value`	`string`	Current effective value.
`source`	`string`	Value source: `default`, `config`, `bootstrap_env`, `sql_runtime`.
`dynamic`	`bool`	`true` if the parameter can be changed without a restart.
`doc`	`string`	Brief description of the parameter.

`sys.databases` Table

List of available databases.

Field	Type	Description
`db_id`	`string`	Unique database identifier.
`name`	`string`	Database name.

`sys.schemas` Table

List of schemas within databases.

Field	Type	Description
`db_id`	`string`	Database identifier.
`schema_name`	`string`	Schema name.

Troubleshooting

Symptom: The sys.tables table returns an empty result.
- Cause: The user does not have permission to view metadata, or no database is selected (if filtering is used).
- Solution: Check access rights (RBAC).
Symptom: A change in sys.settings is not applied.
- Cause: The parameter has dynamic = false or is overridden by an environment variable (source = bootstrap_env).
- Solution: A server restart or a change in configuration/environment variables is required.

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