Developer Options

allow_system_table_mods

Parameter description: Specifies whether the structures of system tables can be modified.

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

It is not recommended to modify the default value of this parameter. If it is set to on, the system tables may be damaged and the database may not start.

Value range: Boolean

• on indicates that the structures of system tables can be modified.
• off indicates that the structures of system tables cannot be modified.

Default value: off

NOTICE: It is not recommended to modify the default value of this parameter. If it is set to on, the system tables may be damaged and the database may not start.

allow_create_sysobject

Parameter description: Sets whether to allow the creation or modification of objects such as functions, stored procedures, synonyms, aggregate functions, operators, and so on, in the system schema. The system schema here refers to the schema that comes with the database after initialization, but does not include the public schema. The oid of system schema is usually less than 16384.

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

Value range: Boolean

• on means that initial users and system administrators are allowed to create or modify objects such as functions, stored procedures, synonyms, aggregate functions, etc., and initial users are allowed to create operators in the system mode. Whether other users are allowed to create these objects, please refer to the privilege requirements of the corresponding mode.

• off means that all users are prohibited from creating or modifying functions, stored procedures, synonyms, aggregate functions, operators and other objects in system mode.

Default value: on

debug_assertions

Parameter description: Specifies whether to enable various assertion checks. This parameter assists in debugging. If you are experiencing strange problems or crashes, set this parameter to on to identify programming defects. To use this parameter, the macro USE_ASSERT_CHECKING must be defined (through the configure option --enable-cassert) during the MogDB compilation.

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

Value range: Boolean

• on indicates that various assertion checks are enabled.
• off indicates that various assertion checks are disabled.

NOTE: This parameter is set to on by default if MogDB is compiled with various assertion checks enabled.

Default value: off

ignore_checksum_failure

Parameter description: Specifies whether to ignore check failures (but still generates an alarm) and continues reading data. Continuing reading data may result in breakdown, damaged data being transferred or hidden, failure of data recovery from remote nodes, or other serious problems. You are not advised to modify the settings.

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

Value range: Boolean

• on indicates that data check errors are ignored.
• off indicates that data check errors are reported.

Default value: off

ignore_system_indexes

Parameter description: Specifies whether to ignore system indexes when reading system tables (but still update the indexes when modifying the tables).

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

NOTICE: This parameter is useful for recovering data from tables whose system indexes are damaged.

Value range: Boolean

• on indicates that system indexes are ignored.
• off indicates that system indexes are not ignored.

Default value: off

post_auth_delay

Parameter description: Specifies the delay in the connection to the server after a successful authentication. Developers can attach a debugger to the server startup process.

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

Value range: an integer ranging from 0 to 2147. The unit is s.

Default value: 0

NOTE: This parameter is used only for commissioning and fault locating. To prevent impact on service running, ensure that the default value 0 is used in the production environment. If this parameter is set to a value other than 0, the cluster status may be abnormal due to a long authentication delay.

pre_auth_delay

Parameter description: Specifies the period of delaying authentication after the connection to the server is started. Developers can attach a debugger to the authentication procedure.

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

Value range: an integer ranging from 0 to 60. The unit is s.

Default value: 0

NOTE: This parameter is used only for commissioning and fault locating. To prevent impact on service running, ensure that the default value 0 is used in the production environment. If this parameter is set to a value other than 0, the cluster status may be abnormal due to a long authentication delay.

trace_notify

Parameter description: Specifies whether to enable the function of generating debugging output for the LISTEN and NOTIFY commands. The level of client_min_messages or log_min_messages must be debug1 or lower so that debugging output can be recorded in the client or server logs, respectively.

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

Value range: Boolean

• on indicates that the function is enabled.
• off indicates that the function is disabled.

Default value: off

trace_recovery_messages

Parameter description: Specifies whether to enable logging of recovery-related debugging output. This parameter allows users to overwrite the normal setting of log_min_messages, but only for specific messages. This is intended for the use in debugging the standby server.

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

Value range: enumerated values. Valid values include debug5, debug4, debug3, debug2, debug1, and log. For details about the parameter values, see log_min_messages.

Default value: log

NOTE:

• log indicates that recovery-related debugging information will not be logged.
• Except the default value log, each of the other values indicates that recovery-related debugging information at the specified level will also be logged. Common settings of log_min_messages enables logs to be unconditionally recorded into server logs.

trace_sort

Parameter description: Specifies whether to print information about resource usage during sorting operations. This parameter is available only when the macro TRACE_SORT is defined during the MogDB compilation. However, TRACE_SORT is currently defined by default.

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

Value range: Boolean

• on indicates that the function is enabled.
• off indicates that the function is disabled.

Default value: off

zero_damaged_pages

Parameter description: Specifies whether to detect a damaged page header that causes MogDB to report an error, aborting the current transaction.

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

Value range: Boolean

Setting this parameter to on causes the system to report a warning, zero out the damaged page, and continue processing. This behavior will destroy data, including all the rows on the damaged page. However, it allows you to bypass the error and retrieve rows from any undamaged pages that may be present in the table. Therefore, it is useful for restoring data if corruption has occurred due to a hardware or software error. In most cases, you are advised not to set this parameter to on if you want to restore data from damaged pages.

Default value: off

remotetype

Parameter description: Specifies the remote connection type.

This parameter cannot be changed.

Value range: enumerated values. Valid values are application, datanode, and internaltool.

Default value: application

max_user_defined_exception

Parameter description: Specifies the maximum number of exceptions. The default value cannot be changed.

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

Value range: an integer. Currently, only the fixed value 1000 is supported.

Default value: 1000

enable_fast_numeric

Parameter description: Specifies whether to enable optimization for numeric data calculation. Calculation of numeric data is time-consuming. Numeric data is converted into int64- or int128-type data to improve numeric data calculation performance.

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

Value range: Boolean

• on or true indicates that optimization for numeric data calculation is enabled.
• off or false indicates that optimization for numeric data calculation is disabled.

Default value: on

enable_compress_spill

Parameter description: Specifies whether to enable the compression function of writing data to disk.

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

Value range: Boolean

• on or true indicates that optimization for writing data to disk is enabled.
• off or false indicates that optimization for writing data to a disk is disabled.

Default value: on

resource_track_log

Parameter description: Specifies the log level of self-diagnosis. Currently, this parameter takes effect only in multi-column statistics.

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

Value range: a string

• summary: Brief diagnosis information is displayed.
• detail: Detailed diagnosis information is displayed.

Currently, the two parameter values differ only when there is an alarm about multi-column statistics not collected. If the parameter is set to summary, such an alarm will not be displayed. If it is set to detail, such an alarm will be displayed.

Default value: summary

show_acce_estimate_detail

Parameter description: The evaluation information is generally used by O&M personnel during maintenance, and it may affect the output display of the EXPLAIN statement. Therefore, this parameter is disabled by default. The evaluation information is displayed only if the verbose option of the EXPLAIN statement is enabled.

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

Value range: Boolean

• on indicates that the evaluation information is displayed in the output of the EXPLAIN statement.
• off indicates that the evaluation information is not displayed in the output of the EXPLAIN statement.

Default value: off

NOTE: The current version does not support database acceleration. Therefore, this parameter does not take effect after being set.

support_batch_bind

Parameter description: Specifies whether to batch bind and execute PBE statements through interfaces such as JDBC, ODBC, and libpq.

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

Value range: Boolean

• on indicates that batch binding and execution are used.
• off indicates that batch binding and execution are not used.

Default value: on

numa_distribute_mode

Parameter description: Specifies the distribution of some shared data and threads among NUMA nodes. This parameter is used to optimize the performance of large-scale ARM servers with multiple NUMA nodes. Generally, you do not need to set this parameter.

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

Value range: a string. The valid values are none and all.

• none indicates that this function is disabled.
• all indicates that some shared data and threads are distributed to different NUMA nodes to reduce the number of remote access times and improve performance. Currently, this function applies only to ARM servers with multiple NUMA nodes. All NUMA nodes must be available for database processes. You cannot select only some NUMA nodes.

NOTE: In the current version, numa_distribute_mode cannot be set to all on the x86 platform.

Default value: none

log_pagewriter

Parameter description: Specifies whether to display the page refresh information of a thread and details about an incremental check point after the incremental check point is enabled. You are not advised to set this parameter to true because a large amount of information will be generated.

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

Value range: Boolean

Default value: on

advance_xlog_file_num

Parameter description: Specifies the number of Xlog files that are periodically initialized in advance in the background. This parameter is used to prevent the Xlog file initialization from affecting the performance during transaction submission. However, such a fault may occur only when the system is overloaded. Therefore, you do not need to set this parameter.

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

Value range: an integer ranging from 0 to 1000000. The value 0 indicates that initialization is not performed in advance. For example, the value 10 indicates that the background thread periodically initializes 10 Xlog files in advance based on the write location of the current xlog.

Default value: 0

enable_beta_opfusion

Parameter description: Specifies whether to accelerate the execution of SQL statements, such as aggregate functions and sorting in TPC-C when enable_opfusion is set to on.

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

Value range: Boolean

• on: enabled.
• off: disabled.

Default value: off

enable_csqual_pushdown

Parameter description: Whether to push the filter down for Rough Check when performing a query.

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

Value range: Boolean

• on indicates that the query should be performed with the filter pushed down to Rough Check.
• off means do not push down the filter and perform Rough Check when querying.

Default value: on

string_hash_compatible

Parameter description: Specifies whether to use the same method to calculate char-type hash values and varchar- or text-type hash values. Based on the setting of this parameter, you can determine whether a redistribution is required when a distribution column is converted from a char-type data distribution into a varchar- or text-type data distribution.

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

Value range: Boolean

• on indicates that the same calculation method is used and a redistribution is not required.
• off indicates that different calculation methods are used and a redistribution is required.

NOTE: Calculation methods differ in the length of input strings used for calculating hash values. (For a char-type hash value, spaces following a string are not counted as the length. For a text- or varchar-type hash value, the spaces are counted.) The hash value affects the calculation result of queries. To avoid query errors, do not modify this parameter during database running once it is set.

Default value: off

pldebugger_timeout

Parameter description: Specifies the timeout interval for the pldebugger server to wait for a response from the debug end.

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 86400. The unit is second.

Default value: 15min

plsql_show_all_error

Parameter description: Specifies whether to skip errors and continue compiling PLPGSQL objects. For details about the impact, see DBE_PLDEVELOPER.

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

Value range: Boolean

Default value: off

ustore_attr

Parameter description: This parameter is mainly used to control the information statistics of the USTORE storage engine table, the type of rollback, the focus of the module (including data, indexes, rollback segments, playback, etc.) run-time data verification, mainly used to assist in research and development problem location.

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

Value range: String, the parameter value is set in key-value mode, the correspondence between key and value and the description are as follows. If more than one key-value are combined, use “;” as separator, for example:

ustore_attr='ustore_verify_level=FAST;ustore_verify_module=UPAGE:UBTREE:UNDO:REDO'.

Description: When ustore_attr sets the parameter value, don't have spaces or other characters before or after the “=” between key and value, for example, ustore_attr='ustore_verify_level = FAST;, the kernel code checking will find that the parameter is not legal, resulting in the parameter setting failure.

• ustore_verify_level: Controls the level of verification.

  Value range: String with case-insensitive values, see the table below for a detailed description.

  Table 1 Meaning of ustore_verify_level values.

  parameter value	meaning
  NONE	NONE means the checksum is turned off, it is recommended to enable it for performance testing scenarios.
  FAST	FAST denotes fast checksums with fewer checksums and minimal performance impacts
  COMPLETE	COMPLETE means full checksum, which has the most checksum content and has a larger performance impact

  Default value: FAST

• ustore_verify_module: Controls the module for verifying.

  Value range: string, set one or more of the values UPAGE, UBTREE, UNDO, REDO, or ALL or NULL (case insensitive) individually. When setting more than one of UPAGE, UBTREE, UNDO, REDO, use “:” as a concatenator. For example ustore_verify_module=UPAGE:UBTREE:UNDO:REDO.

  Table 2 Meaning of ustore_verify_module values.

  parameter value	meaning
  UPAGE	Enables data page validation.
  UBTREE	Enables UBTREE index checking.
  UNDO	Enables rollback segment data validation.
  REDO	Enables data page validation for the REDO process.
  ROACH	Enables data page validation for ROACH backups.
  ALL	Enables data page validation for UPAGE, UBTREE, UNDO, and REDO modules.
  NULL	Disables validation of UPAGE, UBTREE, UNDO, and REDO module data at the same time.

  Default value: UPAGE:UBTREE:UNDO

• index_trace_level: Controls enable index tracking and controls the print level. When enabled, information about eligible index tuples is printed according to different print levels during index scanning.

  Value range: String with values described in the table below.

  Default value: NO

  Table 3 Index_trace_level values.

  parameter value	meaning
  NO	No additional information is printed.
  NORMAL	Prints information about the visible index tuple, including: the index page number where the current index tuple is located, and the offset. The current tuple status. TID and partOid of the current tuple. xmin and xmax information of the current tuple. Current tuple content (if enable_log_tuple is enabled).
  VISIBILITY	On top of NORMAL, prints additional information about index tuples that do not pass the visibility check, and marks them as visible or not.
  SHOWHIKEY	On the basis of VISIBILITY, try to print information about the HIKEY tuple on the page.
  ALL	Prints information about all tuples on the scanned index page.

• enable_log_tuple: Controls whether printing log-level alert messages allows the contents of related tuples to be printed out at the same time for problem troubleshooting and localization.

  Value range: Boolean

  Default value: off

  Note: This parameter is deprecated

• enable_ustore_sync_rollback: Controls whether synchronization rollback is enabled for the USTORE table.

  Value range: Boolean

  Default value: true

• enable_ustore_async_rollback: Controls whether asynchronous rollback is enabled for the USTORE table.

  Value range: Boolean

  Default value: true

• enable_ustore_page_rollback: Controls whether page rollback is enabled for the USTORE table.

  Value range: Boolean

  Default value: true

• enable_ustore_partial_seqscan: Whether to enable partial scanning for the USTORE table.

  Value range: Boolean

  Default value: false

• enable_candidate_buf_usage_count: Enables or disables cache usage counting statistics.

  Value range: Boolean

  Default value: false

• ustats_tracker_naptime: Controls the USTORE table statistics information period.

  Value range: 1~INT_MAX/1000

  Default value: 20, in seconds

• umax_search_length_for_prune: Controls the maximum depth of the USTORE table prune operation search.

  Value range: 1~INT_MAX/1000

  Default value: 10, in times

• ustore_unit_test: R&D White Box Testing Specifying Test Parameters

  Value range: String

  Default value: null

Default value: empty string

NOTICE:

• The ustore_attr parameter should be set with caution and is recommended to be modified with the assistance of an engineer.
• This parameter only applies to USTORE storage engine tables on a centralized or MogDB standalone.

ifnull_all_return_text

Parameter description: When enabled, both ifnull and coalesce will return text to ensure compatibility.

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

Value range: Boolean

Default value: off