SQL support and limits

Resta databases speak the SQLite dialect and store data in the SQLite file format; a few statements that could reach outside the database file are blocked, and every request runs under size and time limits. Most SQLite SQL works unchanged: tables, indexes, views, triggers, CTEs, JSON functions, generate_series, transactions and savepoints.

Engine

Resta runs Turso 0.8, an SQLite-compatible engine written in Rust. Turso tracks SQLite 3.50 and is not yet 100% compatible; its compatibility list shows what is missing. Database files are SQLite files: a snapshot opens in the sqlite3 command-line tool.

Blocked statements

These return the error code BLOCKED, because they could read or write files on the server other than the database’s own:

Statement	Why
`ATTACH`, `DETACH`	Would open another file.
`VACUUM`, `VACUUM INTO`	`VACUUM INTO` writes to any path. Snapshots use it internally.
`CREATE VIRTUAL TABLE`	No modules are offered.
`CREATE TEMP TABLE / VIEW / TRIGGER`	Temp objects live in server memory, outside the size limit.
`load_extension()`, `sqlite_dbpage`	Native code and raw pages.
Most `PRAGMA`s	Only those that touch the database’s own data or session are allowed.

Allowed pragmas: application_id, defer_foreign_keys, encoding, foreign_key_check, foreign_key_list, foreign_keys, freelist_count, function_list, ignore_check_constraints, index_info, index_list, index_xinfo, integrity_check, page_count, page_size, quick_check, recursive_triggers, schema_version (read), table_info, table_list, table_xinfo, user_version. Of these, only application_id, defer_foreign_keys, foreign_keys, ignore_check_constraints, recursive_triggers and user_version can be set.

Limits

Limit	Default	What happens
Database size	1 GiB	Writes past it fail with `SQLITE_FULL`.
Statement time	5 s	The statement fails with `SQLITE_INTERRUPT`.
Request time	30 s	The request fails with `408`.
Request body	10 MiB	`413`.
Response size (pipeline)	10 MiB	`RESPONSE_TOO_LARGE`; use `LIMIT` or the cursor endpoint, which streams.
Statements per pipeline, steps per batch	1,000 each	`400`.
Concurrent requests per server	256	`503`; retry with backoff.

The defaults can be changed: see Configuration.

Writers

Each database allows one writer at a time, as in SQLite. Writes to the same database queue; writes to different databases run in parallel. This is one reason to split data into many databases.

Error codes

SQL errors use SQLite’s codes: SQLITE_CONSTRAINT (with extended_code such as SQLITE_CONSTRAINT_UNIQUE), SQLITE_ERROR, SQLITE_BUSY, SQLITE_FULL, SQLITE_INTERRUPT, plus SQL_PARSE_ERROR, SQL_INPUT_ERROR (wrong argument count), SQL_MANY_STATEMENTS, and BLOCKED.