This section describes the storage format at the level of files and directories. Traditionally, the configuration and data files used by a database cluster are stored together within the cluster's data directory, commonly referred to as PGDATA (after the name of the environment variable that can be used to define it). A common location for PGDATA is /var/lib/pgsql/data. Multiple clusters, managed by different server instances, can exist on the same machine. The PGDATA directory contains several

Namepg_dumpall -- extract a PostgreSQL database cluster into a script file Synopsis pg_dumpall [connection-option...] [option...] Description pg_dumpall is a utility for writing out ("dumping") all PostgreSQL databases of a cluster into one script file. The script file contains SQL commands that can be used as input to psql to restore the databases. It does this by calling pg_dump for each database in a cluster. pg_dumpall also dumps global objects that are common to all databases. (pg_

The first test to see whether you can access the database server is to try to create a database. A running PostgreSQL server can manage many databases. Typically, a separate database is used for each project or for each user. Possibly, your site administrator has already created a database for your use. In that case you can omit this step and skip ahead to the next section. To create a new database, in this example named mydb, you use the following command: $ createdb mydb If this produces no

This module implements a data type seg for representing line segments, or floating point intervals. seg can represent uncertainty in the interval endpoints, making it especially useful for representing laboratory measurements. F.34.1. Rationale The geometry of measurements is usually more complex than that of a point in a numeric continuum. A measurement is usually a segment of that continuum with somewhat fuzzy limits. The measurements come out as intervals because of uncertainty and randomne

The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion constraints on tables. (Column constraints are not treated specially. Every column constraint is equivalent to some table constraint.) Not-null constraints are represented in the pg_attribute catalog, not here. User-defined constraint triggers (created with CREATE CONSTRAINT TRIGGER) also give rise to an entry in this table. Check constraints on domains are stored here, too. Table 50-13. pg_constraint Colu

Each index access method is described by a row in the pg_am system catalog. The pg_am entry specifies a name and a handler function for the access method. These entries can be created and deleted using the CREATE ACCESS METHOD and DROP ACCESS METHOD SQL commands. An index access method handler function must be declared to accept a single argument of type internal and to return the pseudo-type index_am_handler. The argument is a dummy value that simply serves to prevent handler functions from be

In an index scan, the index access method is responsible for regurgitating the TIDs of all the tuples it has been told about that match the scan keys. The access method is not involved in actually fetching those tuples from the index's parent table, nor in determining whether they pass the scan's time qualification test or other conditions. A scan key is the internal representation of a WHERE clause of the form index_key operator constant, where the index key is one of the columns of the index

unaccent is a text search dictionary that removes accents (diacritic signs) from lexemes. It's a filtering dictionary, which means its output is always passed to the next dictionary (if any), unlike the normal behavior of dictionaries. This allows accent-insensitive processing for full text search. The current implementation of unaccent cannot be used as a normalizing dictionary for the thesaurus dictionary. F.44.1. Configuration An unaccent dictionary accepts the following options: RULES is

NameCREATE CAST -- define a new cast Synopsis CREATE CAST (source_type AS target_type) WITH FUNCTION function_name (argument_type [, ...]) [ AS ASSIGNMENT | AS IMPLICIT ] CREATE CAST (source_type AS target_type) WITHOUT FUNCTION [ AS ASSIGNMENT | AS IMPLICIT ] CREATE CAST (source_type AS target_type) WITH INOUT [ AS ASSIGNMENT | AS IMPLICIT ] Description CREATE CAST defines a new cast. A cast specifies how to perform a conversion between two data types. For e

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