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discord9
778f4556a8
Isolated rebase verification of PR #9494. Preserve the reviewed net change; original PR branch remains untouched. Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>
19 lines
2.2 KiB
Markdown
19 lines
2.2 KiB
Markdown
# Query options
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Query options adjust selected behavior for a connection or request; they are not server-wide settings or resource-pool controls.
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| Canonical option | SQL aliases | Values |
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| --- | --- | --- |
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| `query.parallelism` | `query_parallelism`, `query.parallelism` | Integer `1`–`1024`; server default `0` means automatic CPU-based parallelism. This is not a resource-pool limit. |
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| `query.allow_query_fallback` | `query_fallback`, `allow_query_fallback`, `query.allow_query_fallback` (legacy `ALLOW_QUERY_FALLBACK` syntax / `query_fallback` hint also work) | `true` or `false` |
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| `query.enable_remote_dynamic_filter_pushdown` | canonical name | `true` or `false` |
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| `datafusion.optimizer.*` | canonical name | Keys, types, defaults, and validation come from the linked DataFusion version (for example, numeric `max_passes` and Boolean `filter_null_join_keys`). |
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Use `SET query_parallelism = 4` or `SET query.parallelism TO 4`; `SHOW VARIABLES query.parallelism` works in MySQL and PostgreSQL, which also accepts `SHOW query.parallelism`. `SHOW VARIABLES <option>` reports the effective value. Unspecified options inherit engine settings; defaults are automatic parallelism, fallback `false`, and remote dynamic-filter pushdown `true`. Invalid values and unsupported names are errors; unknown third-party MySQL/PostgreSQL initialization settings retain existing tolerance.
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HTTP `X-Greptime-Hints` (for example, `query.parallelism=4`) and gRPC `x-greptime-hints` request metadata set request options; gRPC hints are not a protobuf `Hints` field. The Rust Flight client offers `Database::sql_with_hint` and `flight_request().with_hints`. Hints override session `SET`, including within a multi-statement HTTP request. SQL `SET` lasts for its connection only; `SET LOCAL` transaction-scoped restoration is not implemented.
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`query.enable_remote_dynamic_filter_pushdown` controls propagation across frontend-to-datanode remote queries; it is distinct from DataFusion's native `datafusion.optimizer.enable_dynamic_filter_pushdown`.
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Internal flow/query-reserved keys are not public query options. HTTP response timeout `x-greptime-timeout` defaults to `0` (no deadline); this is a response deadline, not a per-statement or stream/body-processing limit.
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