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Database Object Functions

Updated at:Jul 15, 2020 GMT+08:00

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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    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.

    For example:

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    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

    Note: (1) ANALYZE must be performed before this function is called. (2) Calculate the total size of non-compressed data by estimating the compression rate of column-store tables.

    For example:

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    analyze;
    ANALYZE
    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, index, or 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 the calculated byte size into a size readable to human beings.

    Return type: text

  • pg_size_pretty(numeric)

    Description: Converts the calculated byte size indicated by a numeral into a size readable to human beings.

    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_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.

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, index, sequence, or compressed table, and returns the filenode number allocated to it. The 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 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 the database cluster).

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