Database Object Functions

Database Object Size Functions

Database object size functions calculate the actual disk space used by database objects.

pg_column_size(any)
Description: Specifies the number of bytes used to store a particular value (possibly compressed)
Return type: int
Note: pg_column_size displays the space for storing an independent data value.
```
openGauss=# SELECT pg_column_size(1);
 pg_column_size 
----------------
              4
(1 row)
```
pg_database_size(oid)
Description: Specifies the disk space used by the database with the specified OID.
Return type: bigint
pg_database_size(name)
Description: Specifies the disk space used by the database with the specified name.
Return type: bigint
Note: pg_database_size receives the OID or name of a database and returns the disk space used by the corresponding object.
Example:
```
openGauss=# SELECT pg_database_size('postgres');
 pg_database_size 
------------------
         51590112
(1 row)
```
pg_relation_size(oid)
Description: Specifies the disk space used by the table with a specified OID or index.
Return type: bigint
get_db_source_datasize()
Description: Estimates the total size of non-compressed data in the current database.
Return type: bigint
Remarks: (1) Perform an analysis before this function is called. (2) Calculate the total data capacity in the non-compressed state by estimating the compression rate of the column-store tables.
Example:
```
openGauss=# analyze;
ANALYZE
openGauss=# select get_db_source_datasize();
 get_db_source_datasize
------------------------
            35384925667
(1 row)
```
pg_relation_size(text)
Description: Specifies the disk space used by the table with a specified name or index. The table name can be schema-qualified.
Return type: bigint
pg_relation_size(relation regclass, fork text)
Description: Specifies the disk space used by the specified bifurcating tree ('main', 'fsm', or 'vm') of a certain table or index.
Return type: bigint
pg_relation_size(relation regclass)
Description: Is an abbreviation of pg_relation_size(…, 'main').
Return type: bigint
Note: pg_relation_size receives the OID or name of a table, an index, or a compressed table, and returns the size.
pg_partition_size(oid,oid)
Description: Specifies the disk space used by the partition with a specified OID. The first oid is the OID of the table and the second oid is the OID of the partition.
Return type: bigint
pg_partition_size(text, text)
Description: Specifies the disk space used by the partition with a specified name. The first text is the table name and the second text is the partition name.
Return type: bigint
pg_partition_indexes_size(oid,oid)
Description: Specifies the disk space used by the index of the partition with a specified OID. The first oid is the OID of the table and the second oid is the OID of the partition.
Return type: bigint
pg_partition_indexes_size(text,text)
Description: Specifies the disk space used by the index of the partition with a specified name. The first text is the table name and the second text is the partition name.
Return type: bigint
pg_indexes_size(regclass)
Description: Specifies the total disk space used by the index appended to the specified table.
Return type: bigint
pg_size_pretty(bigint)
Description: Converts a size in bytes expressed as a 64-bit integer into a human-readable format with size units.
Return type: text
pg_size_pretty(numeric)
Description: Converts a size in bytes expressed as a numeric value into a human-readable format with size units.
Return type: text
Note: pg_size_pretty formats the results of other functions into a human-readable format. KB/MB/GB/TB can be used.
pg_table_size(regclass)
Description: Specifies the disk space used by the specified table, excluding indexes (but including TOAST, free space mapping, and visibility mapping).
Return type: bigint
pg_tablespace_size(oid)
Description: Specifies the disk space used by the tablespace with a specified OID.
Return type: bigint
pg_tablespace_size(name)
Description: Specifies the disk space used by the tablespace with a specified name.
Return type: bigint
Note:
pg_tablespace_size receives the OID or name of a database and returns the disk space used by the corresponding object.
pg_total_relation_size(oid)
Description: Specifies the disk space used by the table with a specified OID, including the index and the compressed data.
Return type: bigint
pg_total_relation_size(regclass)
Description: Specifies the total disk space used by the specified table, including all indexes and TOAST data.
Return type: bigint
pg_total_relation_size(text)
Description: Specifies the disk space used by the table with a specified name, including the index and the compressed data. The table name can be schema-qualified.
Return type: bigint
Note: pg_total_relation_size receives the OID or name of a table or a compressed table, and returns the sizes of the data, related indexes, and the compressed table in bytes.

datalength(any)

Description: Specifies the number of bytes used by an expression of a specified data type (data management space, data compression, or data type conversion is not considered).

Return type: int

Note: datalength is used to calculate the space of an independent data value.

Example:

openGauss=# SELECT datalength(1);
datalength
------------
4
(1 row)

The following table lists the supported data types and calculation methods.

Data Type			Storage Space
Numeric data types	Integer types	TINYINT	1
		SMALLINT	2
		INTEGER	4
		BINARY_INTEGER	4
		BIGINT	8
	Arbitrary precision types	DECIMAL	Every four decimal digits occupy two bytes. The digits before and after the decimal point are calculated separately.
		NUMERIC	Every four decimal digits occupy two bytes. The digits before and after the decimal point are calculated separately.
		NUMBER	Every four decimal digits occupy two bytes. The digits before and after the decimal point are calculated separately.
	Sequence integer	SMALLSERIAL	2
		SERIAL	4
		BIGSERIAL	8
		LARGESERIAL	Every four decimal digits occupy two bytes. The digits before and after the decimal point are calculated separately.
	Floating point types	FLOAT4	4
		DOUBLE PRECISION	8
		FLOAT8	8
		BINARY_DOUBLE	8
		FLOAT[(p)]	Every four decimal digits occupy two bytes. The digits before and after the decimal point are calculated separately.
		DEC[(p[,s])]	Every four decimal digits occupy two bytes. The digits before and after the decimal point are calculated separately.
		INTEGER[(p[,s])]	Every four decimal digits occupy two bytes. The digits before and after the decimal point are calculated separately.
Boolean data types	Boolean type	BOOLEAN	1
Character data types	Character types	CHAR	n
		CHAR(n)	n
		CHARACTER(n)	n
		NCHAR(n)	n
		VARCHAR(n)	n
		CHARACTER	Actual number of bytes of a character
		VARYING(n)	Actual number of bytes of a character
		VARCHAR2(n)	Actual number of bytes of a character
		NVARCHAR(n)	Actual number of bytes of a character
		NVARCHAR2(n)	Actual number of bytes of a character
		TEXT	Actual number of bytes of a character
		CLOB	Actual number of bytes of a character
Time data types	Time types	DATE	8
		TIME	8
		TIMEZ	12
		TIMESTAMP	8
		TIMESTAMPZ	8
		SMALLDATETIME	8
		INTERVAL DAY TO SECOND	16
		INTERVAL	16
		RELTIME	4
		ABSTIME	4
		TINTERVAL	12

Database Object Position Functions

pg_relation_filenode(relation regclass)
Description: Specifies the ID of a filenode with the specified relationship.
Return type: oid
Description: pg_relation_filenode receives the OID or name of a table, an index, a sequence, or a compressed table, and returns the number of filenode allocated to it. filenode is the basic component of the file name used by the relationship. For most tables, the result is the same as that of pg_class.relfilenode. For a specified system directory, relfilenode is set to 0 and this function must be used to obtain the correct value. If a relationship that is not stored is transmitted, such as a view, this function returns NULL.
pg_relation_filepath(relation regclass)
Description: Specifies the name of a file path with the specified relationship.
Return type: text
Description: pg_relation_filepath is similar to pg_relation_filenode, except that pg_relation_filepath returns the whole file path name for the relationship (relative to the data directory PGDATA of openGauss).
pg_filenode_relation(tablespace oid, filenode oid)
Description: Obtains the table names corresponding to the tablespace and relfilenode.
Return type: regclass
pg_partition_filenode(partition_oid)
Description: Obtains filenode corresponding to the OID lock of a specified partitioned table.
Return type: oid
pg_partition_filepath(partition_oid)
Description: Specifies the file path name of a partition.
Return type: text

Recycle Bin Object Functions

gs_is_recycle_object(classid, objid, objname)
Description: Determines whether an object is in the recycle bin.
Return type: Boolean