gp_check_functions
The gp_check_functions module implements views that identify missing and orphaned relation files. The module also exposes a user-defined function that you can use to move orphaned files.
The gp_check_functions module is a SynxDB extension.
Installing and Registering the Module
The gp_check_functions module is installed when you install SynxDB. Before you can use the views defined in the module, you must register the gp_check_functions extension in each database in which you want to use the views:
o
CREATE EXTENSION gp_check_functions;
Refer to Installing Additional Supplied Modules for more information.
Checking for Missing and Orphaned Data Files
SynxDB considers a relation data file that is present in the catalog, but not on disk, to be missing. Conversely, when SynxDB encounters an unexpected data file on disk that is not referenced in any relation, it considers that file to be orphaned.
SynxDB provides the following views to help identify if missing or orphaned files exist in the current database:
Consider it a best practice to check for these conditions prior to expanding the cluster or before offline maintenance.
By default, the views in this module are available to PUBLIC.
gp_check_orphaned_files
The gp_check_orphaned_files view scans the default and user-defined tablespaces for orphaned data files. SynxDB considers normal data files, files with an underscore (_) in the name, and extended numbered files (files that contain a .<N> in the name) in this check. gp_check_orphaned_files gathers results from the SynxDB master and all segments.
| Column | Description |
|---|---|
| gp_segment_id | The SynxDB segment identifier. |
| tablespace | The identifier of the tablespace in which the orphaned file resides. |
| filename | The file name of the orphaned data file. |
| filepath | The file system path of the orphaned data file, relative to the data directory of the master or segment. |
Caution Use this view as one of many data points to identify orphaned data files. Do not delete files based solely on results from querying this view.
gp_check_missing_files
The gp_check_missing_files view scans heap and append-optimized, column-oriented tables for missing data files. SynxDB considers only normal data files (files that do not contain a . or an _ in the name) in this check. gp_check_missing_files gathers results from the SynxDB master and all segments.
| Column | Description |
|---|---|
| gp_segment_id | The SynxDB segment identifier. |
| tablespace | The identifier of the tablespace in which the table resides. |
| relname | The name of the table that has a missing data file(s). |
| filename | The file name of the missing data file. |
gp_check_missing_files_ext
The gp_check_missing_files_ext view scans only append-optimized, column-oriented tables for missing extended data files. SynxDB considers both normal data files and extended numbered files (files that contain a .<N> in the name) in this check. Files that contain an _ in the name, and .fsm, .vm, and other supporting files, are not considered. gp_check_missing_files_ext gathers results from the SynxDB segments only.
| Column | Description |
|---|---|
| gp_segment_id | The SynxDB segment identifier. |
| tablespace | The identifier of the tablespace in which the table resides. |
| relname | The name of the table that has a missing extended data file(s). |
| filename | The file name of the missing extended data file. |
Moving Orphaned Data Files
The gp_move_orphaned_files() user-defined function (UDF) moves orphaned files found by the gp_check_orphaned_files view into a file system location that you specify.
The function signature is: gp_move_orphaned_files( <target_directory> TEXT ).
<target_directory> must exist on all segment hosts before you move the files, and the specified directory must be accessible by the gpadmin user. If you specify a relative path for <target_directory>, it is considered relative to the data directory of the master or segment.
SynxDB renames each moved data file to one that reflects the original location of the file in the data directory. The file name format differs depending on the tablespace in which the orphaned file resides:
| Tablespace | Renamed File Format |
|---|---|
| default | seg<num>_base_<database-oid>_<relfilenode> |
| global | seg<num>_global_<relfilenode> |
| user-defined | seg<num>_pg_tblspc_<tablespace-oid>_<gpdb-version>_<database-oid>_<relfilenode> |
For example, if a file named 12345 in the default tablespace is orphaned on primary segment 2,
SELECT * FROM gp_move_orphaned_files('/home/gpadmin/orphaned');
moves and renames the file as follows:
| Original Location | New Location and File Name |
|---|---|
<data_directory>/base/13700/12345 | /home/gpadmin/orphaned/seg2_base_13700_12345 |
gp_move_orphaned_files() returns both the original and the new file system locations for each file that it moves, and also provides an indication of the success or failure of the move operation.
Once you move the orphaned files, you may choose to remove them or to back them up.
Examples
Check for missing and orphaned non-extended files:
SELECT * FROM gp_check_missing_files;
SELECT * FROM gp_check_orphaned_files;
Check for missing extended data files for append-optimized, column-oriented tables:
SELECT * FROM gp_check_missing_files_ext;
Move orphaned files to the /home/gpadmin/orphaned directory:
SELECT * FROM gp_move_orphaned_files('/home/gpadmin/orphaned');