The auto_explain module provides a means for logging execution plans of slow statements automatically, without having to run EXPLAIN by hand. This is especially helpful for tracking down un-optimized queries in large applications. The module provides no SQL-accessible functions. To use it, simply load it into the server. You can load it into an individual session: LOAD 'auto_explain'; (You must be superuser to do that.) More typical usage is to preload it into some or all sessions by includin

Asynchronous commit is an option that allows transactions to complete more quickly, at the cost that the most recent transactions may be lost if the database should crash. In many applications this is an acceptable trade-off. As described in the previous section, transaction commit is normally synchronous: the server waits for the transaction's WAL records to be flushed to permanent storage before returning a success indication to the client. The client is therefore guaranteed that a transactio

PostgreSQL allows columns of a table to be defined as variable-length multidimensional arrays. Arrays of any built-in or user-defined base type, enum type, or composite type can be created. Arrays of domains are not yet supported. 8.15.1. Declaration of Array Types To illustrate the use of array types, we create this table: CREATE TABLE sal_emp ( name text, pay_by_quarter integer[], schedule text[][] ); As shown, an array data type is named by appending square

This section describes several specialized constructs for making multiple comparisons between groups of values. These forms are syntactically related to the subquery forms of the previous section, but do not involve subqueries. The forms involving array subexpressions are PostgreSQL extensions; the rest are SQL-compliant. All of the expression forms documented in this section return Boolean (true/false) results. 9.23.1. IN expression IN (value [, ...]) The right-hand side is a parenthesized

NameANALYZE -- collect statistics about a database Synopsis ANALYZE [ VERBOSE ] [ table_name [ ( column_name [, ...] ) ] ] Description ANALYZE collects statistics about the contents of tables in the database, and stores the results in the pg_statistic system catalog. Subsequently, the query planner uses these statistics to help determine the most efficient execution plans for queries. With no parameter, ANALYZE examines every table in the current database. With a parameter, ANALYZE ex

Table 9-47 shows the operators available for array types. Table 9-47. Array Operators Operator Description Example Result = equal ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3] t <> not equal ARRAY[1,2,3] <> ARRAY[1,2,4] t < less than ARRAY[1,2,3] < ARRAY[1,2,4] t > greater than ARRAY[1,4,3] > ARRAY[1,2,4] t <= less than or equal ARRAY[1,2,3] <= ARRAY[1,2,3] t >= greater than or equal ARRAY[1,4,3] >= ARRAY[1,4,3] t @> contains ARRAY[1,4,3] @> ARRAY[3,1] t &

restore_command (string) The local shell command to execute to retrieve an archived segment of the WAL file series. This parameter is required for archive recovery, but optional for streaming replication. Any %f in the string is replaced by the name of the file to retrieve from the archive, and any %p is replaced by the copy destination path name on the server. (The path name is relative to the current working directory, i.e., the cluster's data directory.) Any %r is replaced by the name of

NameALTER USER MAPPING -- change the definition of a user mapping Synopsis ALTER USER MAPPING FOR { user_name | USER | CURRENT_USER | SESSION_USER | PUBLIC } SERVER server_name OPTIONS ( [ ADD | SET | DROP ] option ['value'] [, ... ] ) Description ALTER USER MAPPING changes the definition of a user mapping. The owner of a foreign server can alter user mappings for that server for any user. Also, a user can alter a user mapping for their own user name if USAGE privilege on the

NameALTER VIEW -- change the definition of a view Synopsis ALTER VIEW [ IF EXISTS ] name ALTER [ COLUMN ] column_name SET DEFAULT expression ALTER VIEW [ IF EXISTS ] name ALTER [ COLUMN ] column_name DROP DEFAULT ALTER VIEW [ IF EXISTS ] name OWNER TO { new_owner | CURRENT_USER | SESSION_USER } ALTER VIEW [ IF EXISTS ] name RENAME TO new_name ALTER VIEW [ IF EXISTS ] name SET SCHEMA new_schema ALTER VIEW [ IF EXISTS ] name SET ( view_option_name [= view_option_value] [, ... ] ) ALTER VIEW

An alternative to the built-in standby mode described in the previous sections is to use a restore_command that polls the archive location. This was the only option available in versions 8.4 and below. In this setup, set standby_mode off, because you are implementing the polling required for standby operation yourself. See the pg_standby module for a reference implementation of this. Note that in this mode, the server will apply WAL one file at a time, so if you use the standby server for queri