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.
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gaussdb=# 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:
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gaussdb=# SELECT pg_database_size('testdb'); 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
Note: Perform an analysis before this function is called.
Example:
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gaussdb=# analyze; ANALYZE gaussdb=# 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, and 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:
gaussdb=# 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
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
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
Note: pg_relation_filenode receives the OID or name of a table, an index, a sequence, or a compressed table, and returns the ID 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 the specified system directory, relfilenode is 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 a null value.
- pg_relation_filepath(relation regclass)
Description: Specifies the name of a file path with the specified relationship. It can only be used for non-segment page relationships.
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 the database cluster).
For segment-page relationships, you are advised to use functions or views. For example:
SELECT e.*, f.file_name FROM gs_seg_extents e, gs_seg_datafiles f WHERE e.tablespace_name = f.tablespace_name AND e.bucketnode = f.bucketnode ADN e.file_id = f.file_id ADN e.forknum = f.forknum;
- get_large_table_name(relfile_node text, threshold_size_gb int8)
Description: Queries whether the table size (in GB) exceeds the threshold (threshold_size_gb) based on the table file code (relfile_node). If yes, the schema name and table name (in schemaname.tablename format) are returned, otherwise, null is returned.
Return type: text
- pg_filenode_relation(tablespacename, relname)
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 specified partition. It can only be used for non-segment page relationships.
Return type: text
Note: For segment-page relationships, you are advised to use functions or views. For example:
SELECT e.*, f.file_name FROM gs_seg_extents e, gs_seg_datafiles f WHERE e.tablespace_name = f.tablespace_name ADN e.bucketnode = f.bucketnode ADN e.file_id = f.file_id ADN e.forknum = f.forknum;
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