These settings control the behavior of the built-in streaming replication feature (see Section 26.2.5). Servers will be either a Master or a Standby server. Masters can send data, while Standby(s) are always receivers of replicated data. When cascading replication (see Section 26.2.7) is used, Standby server(s) can also be senders, as well as receivers. Parameters are mainly for Sending and Standby servers, though some parameters have meaning only on the Master server. Settings may vary across

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

Write-Ahead Logging (WAL) is a standard method for ensuring data integrity. A detailed description can be found in most (if not all) books about transaction processing. Briefly, WAL's central concept is that changes to data files (where tables and indexes reside) must be written only after those changes have been logged, that is, after log records describing the changes have been flushed to permanent storage. If we follow this procedure, we do not need to flush data pages to disk on every trans

PostgreSQL supports the full set of SQL date and time types, shown in Table 8-9. The operations available on these data types are described in Section 9.9. Dates are counted according to the Gregorian calendar, even in years before that calendar was introduced (see Section B.4 for more information). Table 8-9. Date/Time Types Name Storage Size Description Low Value High Value Resolution timestamp [ (p) ] [ without time zone ] 8 bytes both date and time (no time zone) 4713 BC 294276 AD 1 micro

The collation feature allows specifying the sort order and character classification behavior of data per-column, or even per-operation. This alleviates the restriction that the LC_COLLATE and LC_CTYPE settings of a database cannot be changed after its creation. 23.2.1. Concepts Conceptually, every expression of a collatable data type has a collation. (The built-in collatable data types are text, varchar, and char. User-defined base types can also be marked collatable, and of course a domain ov

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

When a table is created, it contains no data. The first thing to do before a database can be of much use is to insert data. Data is conceptually inserted one row at a time. Of course you can also insert more than one row, but there is no way to insert less than one row. Even if you know only some column values, a complete row must be created. To create a new row, use the INSERT command. The command requires the table name and column values. For example, consider the products table from Chapter

NameDECLARE -- define a cursor Synopsis DECLARE name [ BINARY ] [ INSENSITIVE ] [ [ NO ] SCROLL ] CURSOR [ { WITH | WITHOUT } HOLD ] FOR query Description DECLARE allows a user to create cursors, which can be used to retrieve a small number of rows at a time out of a larger query. After the cursor is created, rows are fetched from it using FETCH. Note: This page describes usage of cursors at the SQL command level. If you are trying to use cursors inside a PL/pgSQL function, the

A table expression computes a table. The table expression contains a FROM clause that is optionally followed by WHERE, GROUP BY, and HAVING clauses. Trivial table expressions simply refer to a table on disk, a so-called base table, but more complex expressions can be used to modify or combine base tables in various ways. The optional WHERE, GROUP BY, and HAVING clauses in the table expression specify a pipeline of successive transformations performed on the table derived in the FROM clause. All

Namepostmaster -- PostgreSQL database server Synopsis postmaster [option...] Description postmaster is a deprecated alias of postgres. See Also postgres Prev Next postgres Up Internals