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  2. Data Warehouse Service
  3. Developer Guide
  4. Setting Configuration Parameters
  5. Appendix B: GUC Parameter Description
  6. Miscellaneous Parameters

Miscellaneous Parameters

gin_fuzzy_search_limit

Parameter description: The primary goal of developing GIN indexes was to create support for highly scalable full-text search in DWS, and there are often situations when a full-text search returns a large set of results. Moreover, this often happens when the query contains very frequent words, so that the large result set is not even useful. Since reading many tuples from the disk and sorting them could take a lot of time, this is unacceptable for production. To facilitate controlled execution of such queries, GIN has a configurable soft upper limit on the number of rows returned: the gin_fuzzy_search_limit configuration parameter. It is set to 0 (meaning no limit) by default. If a non-zero limit is set, then the returned set is a subset of the whole result set, chosen at random.

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

Value range: 0 to the maximum int value

Default value: 0

enable_cluster_resize

Parameter description: If an SQL statement involves tables belonging to different groups, you can enable this parameter to push the execution plan of the statement to improve performance.

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

Value range: Boolean

  • on indicates the execution plan of the statement can be pushed.
  • off indicates the execution plan of the statement cannot be pushed.

Default value: off

cstore_insert_mode

Parameter description: Controls the data storage location when the data is imported into an HDFS table. This parameter applies to operations that involve data import, such as INSERT, UPDATE, COPY, DELTAMERGE, and VACUUM FULL.

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

Value range: enumerated values

AUTO: The major part of the imported data is stored in the HDFS storage, and the tail is stored in the delta table.

DELTA: All the imported data is stored in the delta table.

MAIN: All the imported data is stored in the HDFS storage.

Default value: AUTO. You can set other values as the default in the configuration file.

enable_upgrade_merge_lock_mode

Parameter description: If this parameter is set to on, the delta merge operation internally increases the lock level, and errors can be avoided when update and deletion operations are performed at the same time.

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

Value range: Boolean

  • If this parameter is set to on, the delta merge operation internally increases the lock level. In this way, when any two of the DELTAMERGE, UPDATE, and DELETE operations are concurrently performed, an operation can be performed only after the previous one is complete.
  • If this parameter is set to off, and any two of the DELTAMERGE, UPDATE, and DELETE operations are concurrently performed to data in a row in the delta table of the HDFS table, errors will be reported during the later operation, and the operation will stop.

Default value: off

ngram_gram_size

Parameter description: Indicates the length of the ngram parser segmentation.

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

Value range: an integer ranging from 1 to 4

Default value: 2

ngram_grapsymbol_ignore

Parameter description: Specifies whether the ngram parser ignores graphical characters.

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

Value range: Boolean

  • on: Ignores graphical characters.
  • off: Does not ignore graphical characters.

Default value: off

ngram_punctuation_ignore

Parameter description: Specifies whether the ngram parser ignores punctuations.

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

Value range: Boolean

  • on: Ignores punctuations.
  • off: Does not ignore punctuations.

Default value: on

zhparser_multi_duality

Parameter description: Specifies whether Zhparser aggregates segments in long words with duality.

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

Value range: Boolean

  • on: Aggregates segments in long words with duality.
  • off: Does not aggregate segments in long words with duality.

Default value: off

zhparser_multi_short

Parameter description: Specifies whether Zhparser executes long words composite divide.

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

Value range: Boolean

  • on: Executes long words composite divide.
  • off: Does not execute long words composite divide.

Default value: on

zhparser_multi_zall

Parameter description: Specifies whether Zhparser displays all single words individually.

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

Value range: Boolean

  • on: Displays all single words individually.
  • off: Does not display all single words individually.

Default value: off

zhparser_multi_zmain

Parameter description: Specifies whether Zhparser displays important single words separately.

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

Value range: Boolean

  • on: Displays important single words individually.
  • off: Does not display important single words individually.

Default value: off

zhparser_punctuation_ignore

Parameter description: Specifies whether the Zhparser segmentation result ignores special characters including punctuations (\r and \n will not be ignored).

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

Value range: Boolean

  • on: Ignores all the special characters including punctuations.
  • off: Does not ignore all the special characters including punctuations.

Default value: on

zhparser_seg_with_duality

Parameter description: Specifies whether Zhparser aggregates segments in long words with duality.

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

Value range: Boolean

  • on: Aggregates segments with duality.
  • off: Does not aggregate segments in long words with duality.

Default value: off

acceleration_with_compute_pool

Parameter description: Determines whether to use the computing resource pool for acceleration when a foreign OBS table is queried.

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

Value range: Boolean

  • on indicates that the query covering the foreign OBS table is accelerated based on the cost when the computing resource pool is available.
  • off indicates that no query is accelerated using the computing resource pool.

Default value: off

behavior_compat_options

Parameter description: Specifies database compatibility behavior. Multiple items are separated by commas (,).

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

Value range: a string

Default value: empty

NOTE:
  • Currently, only the configuration items specified in Compatibility configuration items are supported.
  • Multiple items are separated by commas (,), for example, set behavior_compat_options='end_month_calculate,display_leading_zero';
Table 1 Compatibility configuration items

Configuration Item

Behavior

display_leading_zero

Specifies how floating point numbers are displayed.

1. If this item is not specified, for a decimal number between -1 and 1, the 0 before the decimal point is not displayed. For example, 0.25 is displayed as .25.

2. If this item is specified, for a decimal number between -1 and 1, the 0 before the decimal point is displayed. For example, 0.25 is displayed as 0.25.

end_month_calculate

Specifies the calculation logic of the add_months function.

Assume that the two parameters of the add_months function are $1 and $2, and that the month of $1 and $2 is $3.

1. If this item is not specified, and the Day of $1 indicates the last day of a month shorter than $3, the Day in the calculation result will equal that in $1. Example:

postgres=# select add_months('2018-02-28',3) from dual;

add_months

---------------------

2018-05-28 00:00:00

(1 row)

2. If this item is specified, and the Day of $1 indicates the last day of a month shorter than $3, the Day in the calculation result will equal that in $3. Example:

postgres=# select add_months('2018-02-28',3) from dual;

add_months

---------------------

2018-05-31 00:00:00

(1 row)

compat_analyze_sample

Specifies the sampling behavior of the ANALYZE operation.

If this item is specified, the sample collected by the ANALYZE operation will be limited to around 30,000 records, controlling CN memory consumption and maintaining the stability of ANALYZE.