Module queries 

SQL schema and statement constants for the SQLite checkpoint saver.

SQLite-specific notes:

• Uses TEXT for JSON columns (SQLite has no native JSONB; json_extract() handles filtering).
• Uses BLOB for binary payloads (Postgres BYTEA).
• Bind parameters use ? placeholders.
• WAL mode is enabled at connection setup for concurrent reads.

Constants

INSERT_CHECKPOINT_WRITES_SQL

Insert checkpoint writes (ignore on conflict). Default for normal per-task writes which should be append-only.

MIGRATIONS

SQL migrations for the checkpoint schema. Applied in order; each migration’s index is recorded in checkpoint_migrations.v.

SELECT_BLOBS_SQL

Fetch all blobs (channel values) for a given checkpoint by joining checkpoint.channel_versions with the blobs table.

SELECT_CHECKPOINT_SQL

Select base columns for a checkpoint row. Channel values and pending writes are fetched separately (SQLite lacks array_agg).

SELECT_WRITES_SQL

Fetch pending writes for a given checkpoint, ordered by task and idx.

UPSERT_CHECKPOINTS_SQL

Upsert a checkpoint, replacing the JSON payload and metadata if the (thread, ns, id) tuple already exists.

UPSERT_CHECKPOINT_BLOBS_SQL

Upsert checkpoint blobs. Blobs are immutable per (channel, version), so on conflict we keep the existing row.

UPSERT_CHECKPOINT_WRITES_SQL

Upsert checkpoint writes (overwrite on conflict). Used for special channels like __error__ whose value may legitimately change.