NameNOTIFY -- generate a notification Synopsis NOTIFY channel [ , payload ] Description The NOTIFY command sends a notification event together with an optional "payload" string to each client application that has previously executed LISTEN channel for the specified channel name in the current database. Notifications are visible to all users. NOTIFY provides a simple interprocess communication mechanism for a collection of processes accessing the same PostgreSQL database. A payload str

PostgreSQL offers data types to store IPv4, IPv6, and MAC addresses, as shown in Table 8-21. It is better to use these types instead of plain text types to store network addresses, because these types offer input error checking and specialized operators and functions (see Section 9.12). Table 8-21. Network Address Types Name Storage Size Description cidr 7 or 19 bytes IPv4 and IPv6 networks inet 7 or 19 bytes IPv4 and IPv6 hosts and networks macaddr 6 bytes MAC addresses When sorting inet or

An index can be defined on more than one column of a table. For example, if you have a table of this form: CREATE TABLE test2 ( major int, minor int, name varchar ); (say, you keep your /dev directory in a database...) and you frequently issue queries like: SELECT name FROM test2 WHERE major = constant AND minor = constant; then it might be appropriate to define an index on the columns major and minor together, e.g.: CREATE INDEX test2_mm_idx ON test2 (major, minor); Currently, only

PostgreSQL's statistics collector is a subsystem that supports collection and reporting of information about server activity. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. It also tracks the total number of rows in each table, and information about vacuum and analyze actions for each table. It can also count calls to user-defined functions and the total time spent in each one. PostgreSQL also supports reporting dynamic information

Another useful tool for monitoring database activity is the pg_locks system table. It allows the database administrator to view information about the outstanding locks in the lock manager. For example, this capability can be used to: View all the locks currently outstanding, all the locks on relations in a particular database, all the locks on a particular relation, or all the locks held by a particular PostgreSQL session. Determine the relation in the current database with the most ungrante

NameMOVE -- position a cursor Synopsis MOVE [ direction [ FROM | IN ] ] cursor_name where direction can be empty or one of: NEXT PRIOR FIRST LAST ABSOLUTE count RELATIVE count count ALL FORWARD FORWARD count FORWARD ALL BACKWARD BACKWARD count BACKWARD ALL Description MOVE repositions a cursor without retrieving any data. MOVE works exactly like the FETCH command, except it only positions the cursor and does not return rows. Th

The most important disk monitoring task of a database administrator is to make sure the disk doesn't become full. A filled data disk will not result in data corruption, but it might prevent useful activity from occurring. If the disk holding the WAL files grows full, database server panic and consequent shutdown might occur. If you cannot free up additional space on the disk by deleting other things, you can move some of the database files to other file systems by making use of tablespaces. See

PostgreSQL has the ability to report the progress of certain commands during command execution. Currently, the only command which supports progress reporting is VACUUM. This may be expanded in the future. 28.4.1. VACUUM Progress Reporting Whenever VACUUM is running, the pg_stat_progress_vacuum view will contain one row for each backend (including autovacuum worker processes) that is currently vacuuming. The tables below describe the information that will be reported and provide information abo

PostgreSQL provides facilities to support dynamic tracing of the database server. This allows an external utility to be called at specific points in the code and thereby trace execution. A number of probes or trace points are already inserted into the source code. These probes are intended to be used by database developers and administrators. By default the probes are not compiled into PostgreSQL; the user needs to explicitly tell the configure script to make the probes available. Currently, th

On most Unix platforms, PostgreSQL modifies its command title as reported by ps, so that individual server processes can readily be identified. A sample display is $ ps auxww | grep ^postgres postgres 15551 0.0 0.1 57536 7132 pts/0 S 18:02 0:00 postgres -i postgres 15554 0.0 0.0 57536 1184 ? Ss 18:02 0:00 postgres: writer process postgres 15555 0.0 0.0 57536 916 ? Ss 18:02 0:00 postgres: checkpointer process postgres 15556 0.0 0.0 57536 916 ?