Optimizer Method Configuration

enable_bitmapscan

Parameter description: Controls the query optimizer's use of bitmap-scan plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

force_bitmapand

Parameter description: Controls the query optimizer's use of BitmapAnd plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: off

enable_hashagg

Parameter description: Controls the query optimizer's use of Hash aggregation plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_hashjoin

Parameter description: Controls the query optimizer's use of Hash-join plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_indexscan

Parameter description: Controls the query optimizer's use of index-scan plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_indexonlyscan

Parameter description: Controls the query optimizer's use of index-only-scan plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_gsiscan

Parameter description: Controls the query optimizer's use of the global secondary index scan plan type. In the current version, global secondary indexes cannot be used for table access by index row ID.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: used.
• off: not used.

Default value: off

enable_material

Parameter description: Controls the query optimizer's use of materialization. It is impossible to suppress materialization entirely, but setting this variable to off prevents the optimizer from inserting materialized nodes.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_mergejoin

Parameter description: Controls the query optimizer's use of merge-join plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: off

enable_nestloop

Parameter description: Controls the query optimizer's use of nested-loop join plan types to fully scan internal tables. It is impossible to suppress nested-loop joins entirely, but setting this variable to off encourages the optimizer to choose other methods if available.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: off

enable_index_nestloop

Parameter description: Controls the query optimizer's use of the index nested-loop join plan types to scan the parameterized indexes of internal tables.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_seqscan

Parameter description: Controls the query optimizer's use of sequential scan plan types. It is impossible to suppress sequential scans entirely, but setting this variable to off encourages the optimizer to choose other methods if available.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_sort

Parameter description: Controls the query optimizer's use of sort methods. It is impossible to suppress explicit sorts entirely, but setting this variable to off encourages the optimizer to choose other methods if available.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_tidscan

Parameter description: Controls the query optimizer's use of Tuple ID (TID) scan plan types.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_kill_query

Parameter description: In CASCADE mode, when a user is deleted, all the objects belonging to the user are deleted. This parameter specifies whether the queries of the objects belonging to the user can be unlocked when the user is deleted.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that the unlocking is allowed.
• off indicates that the unlocking is not allowed.

Default value: off

enable_stream_concurrent_update

Parameter description: Controls the use of stream in concurrent updates. This parameter is restricted by the enable_stream_operator parameter. If concurrent update conflicts occur, an error may be reported. This parameter can be used to control the conflict.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that the optimizer can generate stream plans for the UPDATE statement.
• off indicates that the optimizer can generate only non-stream plans for the UPDATE statement.

Default value: on

enable_stream_operator

Parameter description: Controls the query optimizer's use of stream. When this parameter is set to off, a large number of logs indicating that the stream plans cannot be pushed down are recorded. If you do not need these logs, you are advised to set enable_unshipping_log to off when setting enable_stream_operator to off.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

enable_stream_recursive

Parameter description: Specifies whether to push WITH RECURSIVE join queries to DNs for processing.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that WITH RECURSIVE join queries will be pushed down to DNs.
• off indicates that WITH RECURSIVE join queries will not be pushed down.

Default value: on

max_recursive_times

Parameter description: Specifies the maximum number of WITH RECURSIVE iterations.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: an integer ranging from 0 to 2147483647

Default value: 200

enable_vector_engine

Parameter description: Controls the query optimizer's use of vectorized executor.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_broadcast

Parameter description: Controls the query optimizer's use of broadcast distribution method when it evaluates the cost of stream.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: on

enable_change_hjcost

Parameter description: Specifies whether the optimizer excludes internal table running costs when selecting the Hash Join cost path. If it is set to on, tables with a few records and high running costs are more possible to be selected.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: off

best_agg_plan

This parameter is used to control the type of hashagg plans generated by the query optimizer.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: an integer ranging from 0 to 3.

• 1 indicates that the first plan is forcibly generated.
• 2 indicates that the second plan is forcibly generated if the group by column can be redistributed. Otherwise, the first plan is generated.
• 3 indicates that the third plan is forcibly generated if the group by column can be redistributed. Otherwise, the first plan is generated.
• 0 indicates that the optimizer chooses an optimal plan based on the estimated costs of the three plans above.

Default value: 0

agg_redistribute_enhancement

Parameter description: When the aggregate operation is performed, which contains multiple group by columns and none of the columns is the distribution column, a group by column will be selected for redistribution. This parameter specifies the policy of selecting a redistribution column.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that the column that can be redistributed and evaluates the most distinct value is selected for redistribution.
• off indicates that the first column that can be redistributed is selected for redistribution.

Default value: off

enable_absolute_tablespace

Parameter description: Controls whether the tablespace can use an absolute path.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that an absolute path can be used.
• off indicates that an absolute path cannot be used.

Default value: on

enable_valuepartition_pruning

Parameter description: Specifies whether the DFS partitioned table is dynamically or statically optimized.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that the DFS partitioned table is dynamically or statically optimized.
• off indicates that the DFS partitioned table is not dynamically or statically optimized.

Default value: on

expected_computing_nodegroup

Parameter description: Specifies a compute node group or the way to choose such a group. The node group mechanism is now for internal use only. You do not need to set it.

During join or aggregation operations, a node group can be selected in four modes. In each mode, the specified candidate compute node groups are listed for the optimizer to select the most appropriate one for the current operator.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: a string.

• optimal: The list of candidate compute node groups consists of the node groups where the operator's operation objects are located and the node group that combines all DNs in the node groups on which the current user has the COMPUTE permission.
• query: The list of candidate compute node groups consists of the node groups where the operator's operation objects are located and the node group that combines all DNs in the node groups where base tables involved in the query are located.
• Node group name (when enable_nodegroup_debug is set to off): The list of candidate compute node groups consists of the node groups where the operator's operation objects are located and the specified node group.
• Node group name (when enable_nodegroup_debug is set to on): A specific node group is used as the compute node group.

Default value: query

enable_nodegroup_debug

Parameter description: Specifies whether the optimizer assigns computing workloads to a specific node group when multiple node groups exist in an environment. The node group mechanism is now for internal use only. You do not need to set it.

This parameter takes effect only when expected_computing_nodegroup is set to a specific node group.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that computing workloads are assigned to the node group specified by expected_computing_nodegroup.
• off indicates no node group is specified for computing.

Default value: off

enable_default_index_deduplication

Parameter description: Specifies whether to deduplicate and compress tuples with duplicate key values for a B-tree index by default. The deduplication and compression functions do not take effect for primary key indexes and unique indexes. When there are a large number of indexes with duplicate key values, the deduplication and compression function can effectively reduce the space occupied by indexes. In scenarios where non-unique indexes are used and index key values are seldom repeated or unique, the deduplication and compression function slightly deteriorates the index insertion performance. If the WITH (deduplication set to on/off) syntax is used during index creation, the deduplication parameter is preferentially used to determine whether to use deduplication and compression for the index.

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• off: indicates that the deduplication and compression function is disabled for B-tree indexes. This is the default value.
• on: indicates that the deduplication and compression function is enabled for B-tree indexes.

Default value: off

enable_expr_fusion

Parameter description: Specifies whether to enable the SRF, expression flattening, centralized Seq Scan projection cancellation, transition status of shared aggregate functions, and step number optimization features.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• off: indicates that this function is disabled. This is the default value.
• on: indicates that the SRF, expression flattening, centralized Seq Scan projection cancellation, transition status of shared aggregate functions, and step number optimization features are enabled.

Default value: off

It is supported only in the scenario where query_dop is set to 1.

stream_multiple

Parameter description: Specifies the weight used by the optimizer to calculate the final cost of stream operators.

The base stream cost is multiplied by this weight to obtain the final cost.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

This parameter is applicable only to Redistribute and Broadcast streams.

Value range: a floating point number ranging from 0 to DBL_MAX

Default value: 1

qrw_inlist2join_optmode

Parameter description: Specifies whether to enable inlist-to-join (inlist2join) query rewriting.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: a string.

• disable indicates that the inlist2join query rewriting is disabled.
• cost_base indicates that the cost-based inlist2join query rewriting is enabled.
• rule_base indicates that the forcible rule-based inlist2join query rewriting is enabled.
• A positive integer indicates the threshold of inlist2join query rewriting. If the number of elements in the list is greater than the threshold, the rewriting is performed.

Default value: cost_base

skew_option

Parameter description: Specifies whether an optimization policy is used.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: enumerated values

• off indicates that the policy is disabled.
• normal indicates that a radical policy is used. All possible skews are optimized.
• lazy indicates that a conservative policy is used. Uncertain skews are ignored.

Default value: normal

enable_dngather

Parameter description: Specifies whether to calculate stream plans that meet the threshold on a single DN to reduce the number of planned stream nodes.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: off

dngather_min_rows

Parameter description: Specifies the maximum number of rows that control dngather. Values less than or equal to this parameter value can be calculated on a single DN. The prerequisite is that enable_dngather is enabled.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: a floating point number ranging from –1 to DBL_MAX

Default value: 500.0

cost_weight_index

Parameter description: Specifies the cost weight of index_scan.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: a floating point number ranging from 1e-10 to 1e+10.

Default value: 1

default_limit_rows

Parameter description: Specifies the default estimated number of limit rows for generating genericplan. If this parameter is set to a positive value, the positive value is used as the estimated number of limit rows. If this parameter is set to a negative value, the negative value is converted to a percentage and used as default estimated value, that is, -5 indicates 5%.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: a floating point number ranging from –100 to DBL_MAX

Default value: –10

enforce_a_behavior

Parameter description: Controls the rule matching modes of regular expressions.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that the A matching rule is used.
• off indicates that the POSIX matching rule is used.

Default value: on

enable_force_vector_engine

Parameter description: Specifies whether to forcibly generate vectorized execution plans for a vectorized execution operator if the operator's child node is a non-vectorized operator. When this parameter is set to on, vectorized execution plans are forcibly generated.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that vectorized operators are forcibly generated.
• off indicates that the vectorized operator optimizer determines whether to perform vectorization.

Default value: off

check_implicit_conversions

Parameter description: Specifies whether to check candidate index paths generated for index columns that have implicit type conversions in a query. For details about the application scenarios of this parameter, see section "SQL Tuning Guide > Checking the Performance of Implicit Conversion" in Developer Guide.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: Boolean

• on indicates that a check will be performed for candidate index paths generated for index columns that have implicit type conversion in a query.
• off indicates that a check will not be performed.

Default value: off

When this parameter is set to on, you need to set enable_fast_query_shipping to off so that the mechanism for identifying implicit data type conversion of index columns can take effect.