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 gaussdb 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:
- Call the pgxc_get_residualfiles() function to obtain the name of the database that has residual files.
- 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.
- 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.
- Run the following command to obtain all residual file records of the cluster on the CNs:
1db1=# select * from pgxc_get_residualfiles() order by 4, 6; -- order by is optional.
In the current cluster:
- Residual file records exist in the db1 and db2 databases on the dn_6001_6002 node (active node instance).
- Residual files are displayed in the residualfile column.
- The filepath column lists the files that record residual files. These files are stored in the pg_residualfiles directory under the instance data directory.
- Call the pgxc_verify_residualfiles() function to verify the db1 database.
1db1=# select * from pgxc_verify_residualfiles();
Verification functions are at the database level. Therefore, when a verification function is called in the db1 database, it only verifies residual files in db1.
You can call the get function again to check whether the verification is complete.
1db1=# select * from pgxc_get_residualfiles() order by 4, 6;
As shown in the preceding figure, the residual files in the db1 database have been verified, and the residual files in the db2 database are not verified.
- Call the pgxc_rm_residualfiles() function to delete residual files.
1db1=# select * from pgxc_rm_residualfiles();
- Call the pgxc_get_residualfiles() function again to check the deletion result.
The result shows that the residual files in the db1 database are deleted (isdeleted is marked as t) and the residual files in the db2 database are not deleted.
In addition, nine query results are displayed. Compared with the previous query results, a record for the residual file ending with 9438 is missing. This is because the record file that records the residual file ending with 9438 contains only one record, which is deleted in step 3. If all residual files in a record file are deleted, the record file is also deleted. Deleted files are backed up in the pg_residualfiles/backup directory.
- To delete files from the db2 database, you need to call the verify function in the db2 database and then call the rm function.
- Go to the db2 database and call the verification function.
Query the verification result:
- Call the deletion function:
- Query the deletion result:
All residual files recorded in the record file whose name ends with 8342 have been deleted, so the record file is deleted and backed up in the backup directory. As a result, no records are found.
- Go to the db2 database and call the verification function.
