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Docs: update descriptions and default values (#17473)
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Expand Up @@ -33,34 +33,36 @@ See [Query context](query-context.md) for general query context parameters for a

## SQL query context parameters

Configure Druid SQL query planning using the parameters in the table below.
The following table lists query context parameters you can use to configure Druid SQL planning.
You can override a parameter's default value by setting a runtime property in the format `druid.query.default.context.{query_context_key}`.
For more information, see [Overriding default query context values](../configuration/index.md#overriding-default-query-context-values).

|Parameter|Description|Default value|
|---------|-----------|-------------|
|`sqlQueryId`|Unique identifier given to this SQL query. For HTTP client, it will be returned in `X-Druid-SQL-Query-Id` header.<br/><br/>To specify a unique identifier for SQL query, use `sqlQueryId` instead of [`queryId`](query-context.md). Setting `queryId` for a SQL request has no effect. All native queries underlying SQL use an auto-generated `queryId`.|auto-generated|
|`sqlTimeZone`|Sets the time zone for this connection, which will affect how time functions and timestamp literals behave. Should be a time zone name like "America/Los_Angeles" or offset like "-08:00".|`druid.sql.planner.sqlTimeZone` on the Broker (default: UTC)|
|`sqlStringifyArrays`|When set to true, result columns which return array values will be serialized into a JSON string in the response instead of as an array|true, except for JDBC connections, where it is always false|
|`useApproximateCountDistinct`|Whether to use an approximate cardinality algorithm for `COUNT(DISTINCT foo)`.|`druid.sql.planner.useApproximateCountDistinct` on the Broker (default: true)|
|`useGroupingSetForExactDistinct`|Whether to use grouping sets to execute queries with multiple exact distinct aggregations.|`druid.sql.planner.useGroupingSetForExactDistinct` on the Broker (default: false)|
|`useApproximateTopN`|Whether to use approximate [TopN queries](topnquery.md) when a SQL query could be expressed as such. If false, exact [GroupBy queries](groupbyquery.md) will be used instead.|`druid.sql.planner.useApproximateTopN` on the Broker (default: true)|
|`enableTimeBoundaryPlanning`|If true, SQL queries will get converted to TimeBoundary queries wherever possible. TimeBoundary queries are very efficient for min-max calculation on `__time` column in a datasource |`druid.query.default.context.enableTimeBoundaryPlanning` on the Broker (default: false)|
|`useNativeQueryExplain`|If true, `EXPLAIN PLAN FOR` will return the explain plan as a JSON representation of equivalent native query(s), else it will return the original version of explain plan generated by Calcite.<br /><br />This property is provided for backwards compatibility. It is not recommended to use this parameter unless you were depending on the older behavior.|`druid.sql.planner.useNativeQueryExplain` on the Broker (default: true)|
|`sqlFinalizeOuterSketches`|If false (default behavior in Druid 25.0.0 and later), `DS_HLL`, `DS_THETA`, and `DS_QUANTILES_SKETCH` return sketches in query results, as documented. If true (default behavior in Druid 24.0.1 and earlier), sketches from these functions are finalized when they appear in query results.<br /><br />This property is provided for backwards compatibility with behavior in Druid 24.0.1 and earlier. It is not recommended to use this parameter unless you were depending on the older behavior. Instead, use a function that does not return a sketch, such as `APPROX_COUNT_DISTINCT_DS_HLL`, `APPROX_COUNT_DISTINCT_DS_THETA`, `APPROX_QUANTILE_DS`, `DS_THETA_ESTIMATE`, or `DS_GET_QUANTILE`.|`druid.query.default.context.sqlFinalizeOuterSketches` on the Broker (default: false)|
|`sqlUseBoundAndSelectors`|If false (default behavior if `druid.generic.useDefaultValueForNull=false` in Druid 27.0.0 and later), the SQL planner will use [equality](./filters.md#equality-filter), [null](./filters.md#null-filter), and [range](./filters.md#range-filter) filters instead of [selector](./filters.md#selector-filter) and [bounds](./filters.md#bound-filter). This value must be set to `false` for correct behavior for filtering `ARRAY` typed values. | Defaults to same value as `druid.generic.useDefaultValueForNull`, which is `false`|
|`sqlReverseLookup`|Whether to consider the [reverse-lookup rewrite](lookups.md#reverse-lookup) of the `LOOKUP` function during SQL planning.<br /><br />Calls to `LOOKUP` are only reversed when the number of matching keys is lower than both `inSubQueryThreshold` and `sqlReverseLookupThreshold`.|true|
|`sqlReverseLookupThreshold`|Maximum size of `IN` filter to create when applying a [reverse-lookup rewrite](lookups.md#reverse-lookup). If a `LOOKUP` call matches more keys than this threshold, it is left as-is.<br /><br />If `inSubQueryThreshold` is lower than `sqlReverseLookupThreshold`, the `inSubQueryThreshold` is used as the threshold instead.|10000|
|`sqlPullUpLookup`|Whether to consider the [pull-up rewrite](lookups.md#pull-up) of the `LOOKUP` function during SQL planning.|true|
|`enableJoinLeftTableScanDirect`|This flag applies to queries which have joins. For joins, where left child is a simple scan with a filter, by default, druid will run the scan as a query and the join the results to the right child on broker. Setting this flag to true overrides that behavior and druid will attempt to push the join to data servers instead. Please note that the flag could be applicable to queries even if there is no explicit join. since queries can internally translated into a join by the SQL planner.|`false`|
|`maxNumericInFilters`|Max limit for the amount of numeric values that can be compared for a string type dimension when the entire SQL WHERE clause of a query translates only to an [OR](../querying/filters.md#or) of [Bound filter](../querying/filters.md#bound-filter). By default, Druid does not restrict the amount of of numeric Bound Filters on String columns, although this situation may block other queries from running. Set this parameter to a smaller value to prevent Druid from running queries that have prohibitively long segment processing times. The optimal limit requires some trial and error; we recommend starting with 100. Users who submit a query that exceeds the limit of `maxNumericInFilters` should instead rewrite their queries to use strings in the `WHERE` clause instead of numbers. For example, `WHERE someString IN (‘123’, ‘456’)`. This value cannot exceed the set system configuration `druid.sql.planner.maxNumericInFilters`. This value is ignored if `druid.sql.planner.maxNumericInFilters` is not set explicitly.|`-1`|
|`inFunctionThreshold`| At or beyond this threshold number of values, SQL `IN` is converted to [`SCALAR_IN_ARRAY`](sql-functions.md#scalar_in_array). A threshold of 0 forces this conversion in all cases. A threshold of [Integer.MAX_VALUE] disables this conversion. The converted function is eligible for fewer planning-time optimizations, which speeds up planning, but may prevent certain planning-time optimizations.| `100`|
|`inFunctionExprThreshold`|At or beyond this threshold number of values, SQL `IN` is eligible for execution using the native function `scalar_in_array` rather than an <code>&#124;&#124;</code> of `==`, even if the number of values is below `inFunctionThreshold`. This property only affects translation of SQL `IN` to a [native expression](math-expr.md). It does not affect translation of SQL `IN` to a [native filter](filters.md). This property is provided for backwards compatibility purposes, and may be removed in a future release.|`2`|
|`inSubQueryThreshold`|At or beyond this threshold number of values, SQL `IN` is converted to `JOIN` on an inline table. `inFunctionThreshold` takes priority over this setting. A threshold of 0 forces usage of an inline table in all cases where the size of a SQL `IN` is larger than `inFunctionThreshold`. A threshold of `2147483647` disables the rewrite of SQL `IN` to `JOIN`. |`2147483647`|
|`sqlQueryId`|SQL query ID. For HTTP client, Druid returns it in the `X-Druid-SQL-Query-Id` header.<br/><br/>To specify a SQL query ID, use `sqlQueryId` instead of [`queryId`](query-context.md). Setting `queryId` for a SQL request has no effect. All native queries underlying SQL use an auto-generated `queryId`.|auto-generated|
|`sqlTimeZone`|Time zone for a connection. For example, "America/Los_Angeles" or an offset like "-08:00". This parameter affects how time functions and timestamp literals behave. |UTC|
|`sqlStringifyArrays`|If `true`, Druid serializes result columns with array values as JSON strings in the response instead of arrays.|`true`, except for JDBC connections, where it's always `false`|
|`useApproximateCountDistinct`|Whether to use an approximate cardinality algorithm for `COUNT(DISTINCT foo)`.|`true`|
|`useGroupingSetForExactDistinct`|Whether to use grouping sets to execute queries with multiple exact distinct aggregations.|`false`|
|`useApproximateTopN`|If `true`, Druid converts SQL queries to approximate [TopN queries](topnquery.md) wherever possible. If `false`, Druid uses exact [GroupBy queries](groupbyquery.md) instead.|`true`|
|`enableTimeBoundaryPlanning`|If `true`, Druid converts SQL queries to [time boundary queries](timeboundaryquery.md) wherever possible. Time boundary queries are very efficient for min-max calculation on the `__time` column in a datasource. |`false`|
|`useNativeQueryExplain`|If `true`, `EXPLAIN PLAN FOR` returns the explain plan as a JSON representation of equivalent native query, else it returns the original version of explain plan generated by Calcite.<br /><br />This property is provided for backwards compatibility. We don't recommend setting this parameter unless your application depends on the older behavior.|`true`|
|`sqlFinalizeOuterSketches`|If `false` (default behavior in Druid 25.0.0 and later), `DS_HLL`, `DS_THETA`, and `DS_QUANTILES_SKETCH` return sketches in query results. If `true` (default behavior in Druid 24.0.1 and earlier), Druid finalizes sketches from these functions when they appear in query results.<br /><br />This property is provided for backwards compatibility with behavior in Druid 24.0.1 and earlier. We don't recommend setting this parameter unless your application uses Druid 24.0.1 or earlier. Instead, use a function that doesn't return a sketch, such as `APPROX_COUNT_DISTINCT_DS_HLL`, `APPROX_COUNT_DISTINCT_DS_THETA`, `APPROX_QUANTILE_DS`, `DS_THETA_ESTIMATE`, or `DS_GET_QUANTILE`.|`false`|
|`sqlUseBoundAndSelectors`|If `false` (default behavior if `druid.generic.useDefaultValueForNull=false` in Druid 27.0.0 and later), the SQL planner uses [equality](./filters.md#equality-filter), [null](./filters.md#null-filter), and [range](./filters.md#range-filter) filters instead of [selector](./filters.md#selector-filter) and [bounds](./filters.md#bound-filter). For filtering `ARRAY` typed values, `sqlUseBoundAndSelectors` must be `false`. | Defaults to same value as `druid.generic.useDefaultValueForNull`.|
|`sqlReverseLookup`|Whether to consider the [reverse-lookup rewrite](lookups.md#reverse-lookup) of the `LOOKUP` function during SQL planning.<br /><br />Druid reverses calls to `LOOKUP` only when the number of matching keys is lower than both `inSubQueryThreshold` and `sqlReverseLookupThreshold`.|`true`|
|`sqlReverseLookupThreshold`|Maximum size of `IN` filter to create when applying a [reverse-lookup rewrite](lookups.md#reverse-lookup). If a `LOOKUP` call matches more keys than the specified threshold, it remains unchanged.<br /><br />If `inSubQueryThreshold` is lower than `sqlReverseLookupThreshold`, Druid uses `inSubQueryThreshold` threshold instead.|10000|
|`sqlPullUpLookup`|Whether to consider the [pull-up rewrite](lookups.md#pull-up) of the `LOOKUP` function during SQL planning.|`true`|
|`enableJoinLeftTableScanDirect`|This parameter applies to queries with joins. By default, when the left child is a simple scan with a filter, Druid runs the scan as a query, then joins it with the right child on the Broker. Setting this parameter to `true` overrides that behavior and pushes the join to the data servers instead. Even if a query doesn't explicitly include a join, this parameter may still apply since the SQL planner can translate the query into a join internally.|`false`|
|`maxNumericInFilters`|Max limit for the amount of numeric values that Druid can compare for a string type dimension when the entire SQL WHERE clause of a query translates only to an [OR](../querying/filters.md#or) of [bound filter](../querying/filters.md#bound-filter). By default, Druid doesn't restrict the amount of numeric bound filters on string columns, although this situation may block other queries from running. Set this parameter to a smaller value to prevent Druid from running queries that have prohibitively long segment processing times. The optimal limit requires some trial and error. We recommend starting with 100. Users who submit a query that exceeds the limit of `maxNumericInFilters` should rewrite their queries to use strings in the `WHERE` clause instead of numbers. For example, `WHERE someString IN (‘123’, ‘456’)`. This value can't exceed the set system configuration `druid.sql.planner.maxNumericInFilters`. If `druid.sql.planner.maxNumericInFilters` isn't set explicitly, Druid ignores this value.|`-1`|
|`inFunctionThreshold`| At or beyond this threshold number of values, Druid converts SQL `IN` to [`SCALAR_IN_ARRAY`](sql-functions.md#scalar_in_array). A threshold of 0 forces this conversion in all cases. A threshold of `Integer.MAX_VALUE` disables this conversion. The converted function is eligible for fewer planning-time optimizations, which speeds up planning, but may prevent certain planning-time optimizations.| `100`|
|`inFunctionExprThreshold`|At or beyond this threshold number of values, SQL `IN` is eligible for execution using the native function `scalar_in_array` rather than an <code>&#124;&#124;</code> of `==`, even if the number of values is below `inFunctionThreshold`. This property only affects translation of SQL `IN` to a [native expression](math-expr.md). It doesn't affect translation of SQL `IN` to a [native filter](filters.md). This property is provided for backwards compatibility purposes, and may be removed in a future release.|`2`|
|`inSubQueryThreshold`|At or beyond this threshold number of values, Druid converts SQL `IN` to `JOIN` on an inline table. `inFunctionThreshold` takes priority over this setting. A threshold of 0 forces usage of an inline table in all cases where the size of a SQL `IN` is larger than `inFunctionThreshold`. A threshold of `2147483647` disables the rewrite of SQL `IN` to `JOIN`. |`2147483647`|

## Setting the query context
The query context parameters can be specified as a "context" object in the [JSON API](../api-reference/sql-api.md) or as a [JDBC connection properties object](../api-reference/sql-jdbc.md).
See examples for each option below.
## Set the query context

### Example using JSON API
You can configure query context parameters in the `context` object of the [JSON API](../api-reference/sql-api.md) or as a [JDBC connection properties object](../api-reference/sql-jdbc.md).

The following example shows how to set a query context parameter using the JSON API:

```
{
Expand All @@ -71,7 +73,7 @@ See examples for each option below.
}
```

### Example using JDBC
The following example shows how to set query context parameters using JDBC:

```java
String url = "jdbc:avatica:remote:url=http://localhost:8082/druid/v2/sql/avatica/";
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