Residual File Management Functions

Functions for Obtaining the Residual File List

• pg_get_residualfiles()

  Description: Obtains all residual file records of the current node. This function is an instance-level function and is irrelevant to the current database. It can run on any instance.

  Parameter type: none

  Return type: record

  The following table describes return columns.

  Column	Type	Description
  isverified	bool	Verified or not
  isdeleted	bool	Deleted or not
  dbname	text	Database name
  residualfile	text	Data file path
  filepath	text	Residual file path
  notes	text	Notes

  Example:

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  select * from pg_get_residualfiles(); isverified | isdeleted | dbname | residualfile | filepath | notes ------------+-----------+--------+-------------------+---------------------------+------- f | f | db2 | base/49155/114691 | pgrf_20200908160211441546 | f | f | db2 | base/49155/114694 | pgrf_20200908160211441546 | f | f | db2 | base/49155/114696 | pgrf_20200908160211441546 | (3 rows)

• pgxc_get_residualfiles()

  Description: Unified CN query function of pg_get_residualfiles() This function is a cluster-level function and is irrelevant to the current database. It runs on CNs.

  Parameter type: none

  Return type: record

  The following table describes return columns.

  Column	Type	Description
  nodename	text	Node name
  isverified	bool	Verified or not
  isdeleted	bool	Deleted or not
  dbname	text	Database name
  residualfile	text	Data file path
  filepath	text	Residual file path
  notes	text	Notes

  Example:

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  select * from pgxc_get_residualfiles(); nodename | isverified | isdeleted | dbname | residualfile | filepath | notes --------------+------------+-----------+----------+-------------------+---------------------------+------- cn_5001 | f | f | gaussdb | base/15092/32803 | pgrf_20200910170129360401 | dn_6001_6002 | f | f | db2 | base/49155/114691 | pgrf_20200908160211441546 | dn_6001_6002 | f | f | db2 | base/49155/114694 | pgrf_20200908160211441546 | dn_6001_6002 | f | f | db2 | base/49155/114696 | pgrf_20200908160211441546 | (4 rows)

Functions for Verifying Residual Files

• pg_verify_residualfiles(filepath)

  Description: Verifies whether the file recorded in the parameter specified file is a residual file. This function is an instance-level function and is related to the current database. It can run on any instance.

  Parameter type: text

  Return type: bool

  The following table describes return columns.

  Column	Type	Description
  isverified	bool	Verification completed or not

  Example:

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  select * from pg_verify_residualfiles('pgrf_20200908160211441546'); isverified ------------ t (1 row)

  

  This function only verifies whether the recorded file is a residual file in the current database. If the recorded file is not in the current database, the verification is not applicable.

• pg_verify_residualfiles()

  Description: Verifies whether recorded files on all residual file lists of the current instance are residual files. This function is an instance-level function and is related to the current database. It can run on any instance.

  Parameter type: none

  Return type: record

  The following table describes return columns.

  Column	Type	Description
  result	bool	Verification completed or not
  filepath	text	Residual file path
  notes	text	Notes

  Example:

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  select * from pg_verify_residualfiles(); result | filepath | notes --------+---------------------------+------- t | pgrf_20200908160211441546 | (1 row)

  

  This function only verifies whether the recorded file is a residual file in the current database. If the recorded file is not in the current database, the verification is not applicable.

• pgxc_verify_residualfiles()

  Description: Unified CN query function of pg_verify_residualfiles() This function is a cluster-level function and is related to the current database. It runs on CNs.

  Parameter type: none

  Return type: record

  The following table describes return columns.

  Column	Type	Description
  nodename	text	Node name
  result	bool	Verification completed or not
  filepath	text	Residual file path
  notes	text	Notes

  Example:

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  select * from pgxc_verify_residualfiles(); nodename | result | filepath | notes --------------+--------+---------------------------+------- cn_5001 | t | pgrf_20200910170129360401 | dn_6001_6002 | t | pgrf_20200908160211441546 | (2 rows)

  

  This function only verifies whether the recorded file is a residual file in the current database. If the recorded file is not in the current database, the verification is not applicable.

• pg_is_residualfiles(residualfile)

  Description: Queries whether a specified relfilenode is a residual file in the current database. This function is an instance-level function and is related to the current database. It can run on any instance.

  Parameter type: text

  Return type: bool

  The following table describes return columns.

  Column	Type	Description
  result	bool	Residual file or not

  Example:

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  select * from pg_is_residualfiles('base/49155/114691'); result -------- t (1 row)

  

  This function only verifies whether the recorded file is a residual file in the current database. If the recorded file is not in the current database, it is verified as a residual file.

  For example, the file base/15092/14790 is not regarded as a residual file in a postgres database, but it is regarded as a residual file in other databases.

  select * from pg_is_residualfiles('base/15092/14790');

  result

  --------

  f

  (1 row)

  \c db2

  db2=# select * from pg_is_residualfiles('base/15092/14790');

  result

  --------

  t

  (1 row)

Functions for Deleting Residual Files

• pg_rm_residualfiles(filepath)

  Description: Deletes files from a specified residual file list on the current instance. This function is an instance-level function and is irrelevant to the current database. It can run on any instance.

  Parameter type: text

  Return type: record

  The following table describes return columns.

  Column	Type	Description
  result	bool	Deletion completed or not

  Example:

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  select * from pg_rm_residualfiles('pgrf_20200908160211441599'); result -------- t (1 row)

  

  1. Residual files can be deleted only after verification using the pg_verify_residualfiles() function.

  2. All verified files, regardless which database they are in, will be deleted.

  3. If all files recorded in the specified file have been deleted, the specified file will be removed and backed up in the $PGDATA/pg_residualfile/backup directory.

• pg_rm_residualfiles()

  Description: Deletes all files recorded on all residual file lists on the current instance. This function is an instance-level function and is irrelevant to the current database. It can run on any instance.

  Parameter type: none

  Return type: record

  The following table describes return columns.

  Column	Type	Description
  result	bool	Deleted or not
  filepath	text	Residual file path
  notes	text	Notes

  Example:

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  select * from pg_rm_residualfiles(); result | filepath | notes --------+---------------------------+------- t | pgrf_20200908160211441546 | (1 row)

  

  • Residual files can be deleted only after verification using the pg_verify_residualfiles() function.
  • All verified files, regardless which database they are in, will be deleted.
  • If all files recorded in the specified file have been deleted, the specified file will be removed and backed up in the $PGDATA/pg_residualfile/backup directory.

• pgxc_rm_residualfiles()

  Description: Unified CN query function of pgxc_rm_residualfiles. This function is a cluster-level function and is irrelevant to the current database. It runs on CNs.

  Parameter type: none

  Return type: record

  The following table describes return columns.

  Column	Type	Description
  nodename	text	Node name
  result	bool	Deletion completed or not
  filepath	text	Residual file path
  notes	text	Notes

  Example:

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  select * from pgxc_rm_residualfiles(); nodename | result | filepath | notes --------------+--------+---------------------------+------- cn_5001 | t | pgrf_20200910170129360401 | dn_6001_6002 | t | pgrf_20200908160211441546 | (2 rows)

Using the Residual File Management Function:

Procedure:

1. Call the pgxc_get_residualfiles() function to obtain the name of the database that has residual files.
2. Go to the databases where residual files exist and call the pgxc_verify_residualfiles() function to verify the residual files recorded in the current database.
3. Call the pgxc_rm_residualfiles() function to delete all the verified residual files.

The pgxc residual file management function only operates on the CN and the current primary DN, and does not verify or clear residual files on the standby DN. Therefore, after the primary DN is cleared, you need to clear residual files on the standby DN or build the standby DN in a timely manner. This prevents residual files on the standby DN from being copied back to the primary DN due to incremental build after a primary/standby switchover.

Example:

The following example uses two user-created databases, db1 and db2.