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4.10.1 Statement Behavior

search_path (string)

This variable specifies the order in which schemas are searched when an object (table, data type, function, etc.) is referenced by a simple name with no schema component. When there are objects of identical names in different schemas, the one found first in the search path is used. An object that is not in any of the schemas in the search path can only be referenced by specifying its containing schema with a qualified (dotted) name. The value for search_path has to be a comma-separated list of schema names. If one of the list items is the special value $user, then the schema having the name returned by SESSION_USER is substituted, if there is such a schema. (If not, $user is ignored.) The system catalog schema, pg_catalog, is always searched, whether it is mentioned in the path or not. If it is mentioned in the path then it will be searched in the specified order. If pg_catalog is not in the path then it will be searched before searching any of the path items. It should also be noted that the temporary-table schema, pg_temp_nnn, is implicitly searched before any of these. When objects are created without specifying a particular target schema, they will be placed in the first schema listed in the search path. An error is reported if the search path is empty. The default value for this parameter is '"$user", public' (where the second part will be ignored if there is no schema named public). This supports shared use of a database (where no users have private schemas, and all share use of public), private per-user schemas, and combinations of these. Other effects can be obtained by altering the default search path setting, either globally or per-user. The current effective value of the search path can be examined via the SQL function current_schemas(). This is not quite the same as examining the value of search_path, since current_schemas() shows how the requests appearing in search_path were resolved. For more information on schema handling, see Volume 1: Schemas.

default_tablespace (string)

This variable specifies the default tablespace in which to create objects (tables and indexes) when a CREATE command does not explicitly specify a tablespace. The value is either the name of a tablespace, or an empty string to specify using the default tablespace of the current database. If the value does not match the name of any existing tablespace, PostgreSQL will automatically use the default tablespace of the current database. For more information on tablespaces, see section 6.6 Tablespaces.

check_function_bodies (boolean)

This parameter is normally on. When set to off, it disables validation of the function body string during CREATE FUNCTION. Disabling validation is occasionally useful to avoid problems such as forward references when restoring function definitions from a dump.

default_transaction_isolation (string)

Each SQL transaction has an isolation level, which can be either “read uncommitted”, “read committed”, “repeatable read”, or “serializable”. This parameter controls the default isolation level of each new transaction. The default is “read committed”. Consult Volume 1: Concurrency Control and SET TRANSACTION for more information.

default_transaction_read_only (boolean)

A read-only SQL transaction cannot alter non-temporary tables. This parameter controls the default read-only status of each new transaction. The default is off (read/write). Consult SET TRANSACTION for more information.

statement_timeout (integer)

Abort any statement that takes over the specified number of milliseconds, starting from the time the command arrives at the server from the client. If log_min_error_statement is set to ERROR or lower, the statement that timed out will also be logged. A value of zero (the default) turns off the limitation.

vacuum_freeze_min_age (integer)

Specifies the cutoff age (in transactions) that VACUUM should use to decide whether to replace transaction IDs with FrozenXID while scanning a table. The default is 100 million transactions. Although users can set this value anywhere from zero to one billion, VACUUM will silently limit the effective value to half the value of autovacuum_freeze_max_age, so that there is not an unreasonably short time between forced autovacuums. For more information see section 9.1.3 Preventing transaction ID wraparound failures.