PostgreSQL functions

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# LXXXI. PostgreSQL functions

# Introduction

PostgreSQL database is Open Source product and available without cost. Postgres, developed originally in the UC Berkeley Computer Science Department, pioneered many of the object-relational concepts now becoming available in some commercial databases. It provides SQL92/SQL99 language support, transaction integrity and type extensibility. PostgreSQL is an open source descendant of this original Berkeley code.

# Requirements

To use PostgreSQL support, you need PostgreSQL 6.5 or later, PostgreSQL 7.0 or later to enable all PostgreSQL module features. PostgreSQL supports many character encoding including multibyte character encoding. The current version and more information about PostgreSQL is available at http://www.postgresql.org/.

# Installation

In order to enable PostgreSQL support, `--with-pgsql[=DIR]` is required when you compile PHP. If shared object module is available, PostgreSQL module may be loaded using extension directive in `php.ini` or dl() function.

# Runtime Configuration

The behaviour of these functions is affected by settings in `php.ini`.

Table 1. PostgreSQL configuration options

Name | Default | Changeable
--- | --- | ---
pgsql.allow_persistent | "1" | PHP_INI_SYSTEM
pgsql.max_persistent | "-1" | PHP_INI_SYSTEM
pgsql.max_links | "-1" | PHP_INI_SYSTEM
pgsql.auto_reset_persistent | "0" | PHP_INI_SYSTEM
pgsql.ignore_notice | "0" | PHP_INI_ALL
pgsql.log_notice | "0" | PHP_INI_ALL

For further details and definition of the PHP_INI_* constants see ini_set().

Here is a short explanation of the configuration directives.

`pgsql.allow_persistent` boolean

  Whether to allow persistent Postgres connections.

`pgsql.max_persistent` integer

  The maximum number of persistent Postgres connections per process.

`pgsql.max_links` integer

  The maximum number of Postgres connections per process, including persistent connections.

# How to use and hints

Warning
Using the PostgreSQL module with PHP 4.0.6 is not recommended due to a bug in the notice message handling code. Use 4.1.0 or later.

Warning
PostgreSQL function names will be changed in 4.2.0 release to confirm to current coding standards. Most of new names will have additional underscores, e.g. pg_lo_open(). Some functions are renamed to different name for consistency. e.g. pg_exec() to pg_query(). Older names can be used in 4.2.0 and a few releases from 4.2.0, but they may be deleted in the future. Table 2. Function names changed
Old name | New name
--- | ---
pg_exec() | pg_query()
pg_getlastoid() | pg_last_oid()
pg_cmdtuples() | pg_affected_rows()
pg_numrows() | pg_num_rows()
pg_numfields() | pg_num_fields()
pg_fieldname() | pg_field_name()
pg_fieldsize() | pg_field_size()
pg_fieldnum() | pg_field_num()
pg_fieldprtlen() | pg_field_prtlen()
pg_fieldisnull() | pg_field_is_null()
pg_freeresult() | pg_free_result()
pg_result() | pg_fetch_result()
pg_loreadall() | pg_lo_read_all()
pg_locreate() | pg_lo_create()
pg_lounlink() | pg_lo_unlink()
pg_loopen() | pg_lo_open()
pg_loclose() | pg_lo_close()
pg_loread() | pg_lo_read()
pg_lowrite() | pg_lo_write()
pg_loimport() | pg_lo_import()
pg_loexport() | pg_lo_export()
The old pg_connect()/pg_pconnect() syntax will be deprecated to support asynchronous connections in the future. Please use a connection string for pg_connect() and pg_pconnect().

Not all functions are supported by all builds. It depends on your libpq (The PostgreSQL C Client interface) version and how libpq is compiled. If there is missing function, libpq does not support the feature required for the function.

It is also important that you use newer libpq than PostgreSQL Server to be connected. If you use libpq older than PostgreSQL Server expects, you may have problems.

Since version 6.3 (03/02/1998) PostgreSQL uses unix domain sockets by default. TCP port will NOT be opened by default. A table is shown below describing these new connection possibilities. This socket will be found in `/tmp/.s.PGSQL.5432`. This option can be enabled with the '-i' flag to postmaster and it's meaning is: "listen on TCP/IP sockets as well as Unix domain sockets".

Table 3. Postmaster and PHP

Postmaster | PHP | Status
--- | --- | ---
postmaster & | pg_connect("dbname=MyDbName"); | OK
postmaster -i & | pg_connect("dbname=MyDbName"); | OK
postmaster & | pg_connect("host=localhost dbname=MyDbName"); | Unable to connect to PostgreSQL server: connectDB() failed: Is the postmaster running and accepting TCP/IP (with -i) connection at 'localhost' on port '5432'? in /path/to/file.php on line 20.
postmaster -i & | pg_connect("host=localhost dbname=MyDbName"); | OK

A connection to PostgreSQL server can be established with the following value pairs set in the command string: $conn = pg_connect("host=myHost port=myPort tty=myTTY options=myOptions dbname=myDB user=myUser password=myPassword ");

The previous syntax of: $conn = pg_connect ("host", "port", "options", "tty", "dbname") has been deprecated.

Environmental variables affect PostgreSQL server/client behavior. For example, PostgreSQL module will lookup PGHOST environment variable when the hostname is omitted in the connection string. Supported environment variables are different from version to version. Refer to PostgreSQL Programmer's Manual (libpq - Environment Variables) for details.

Make sure you set environment variables for appropriate user. Use `$_ENV` or getenv() to check which environment variables are available to the current process.

Example 1. Setting default parameters
    PGHOST=pgsql.example.com
    PGPORT=7890
    PGDATABASE=web-system
    PGUSER=web-user
    PGPASSWORD=secret
    PGDATESTYLE=ISO
    PGTZ=JST
    PGCLIENTENCODING=EUC-JP

    export PGHOST PGPORT PGDATABASE PGUSER PGPASSWORD PGDATESTYLE PGTZ PGCLIENTENCODING

# Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

`PGSQL_ASSOC` (integer)

`PGSQL_NUM` (integer)

`PGSQL_BOTH` (integer)

`PGSQL_CONNECTION_BAD` (integer)

`PGSQL_CONNECTION_OK` (integer)

`PGSQL_SEEK_SET` (integer)

`PGSQL_SEEK_CUR` (integer)

`PGSQL_SEEK_END` (integer)

`PGSQL_ESCAPE_STRING` (integer)

`PGSQL_ESCAPE_BYTEA` (integer)

`PGSQL_EMPTY_QUERY` (integer)

`PGSQL_COMMAND_OK` (integer)

`PGSQL_TUPLES_OK` (integer)

`PGSQL_COPY_OUT` (integer)

`PGSQL_COPY_IN` (integer)

`PGSQL_BAD_RESPONSE` (integer)

`PGSQL_NONFATAL_ERROR` (integer)

`PGSQL_FATAL_ERROR` (integer)

# Examples

Starting with PostgreSQL 7.1.0, you can store up to 1GB into a field of type text. In older versions, this was limited to the block size (default was 8KB, maximum was 32KB, defined at compile time)

To use the large object (lo) interface, it is required to enclose large object functions within a transaction block. A transaction block starts with a SQL statement BEGIN and if the transaction was valid ends with COMMIT or END. If the transaction fails the transaction should be closed with ROLLBACK or ABORT.

Example 2. Using Large Objects
    <?php
        $database = pg_connect ("dbname=jacarta");
        pg_query ($database, "begin");
        $oid = pg_lo_create ($database);
        echo "$oid\n";
        $handle = pg_lo_open ($database, $oid, "w");
        echo "$handle\n";
        pg_lo_write ($handle, "large object data");
        pg_lo_close ($handle);
        pg_query ($database, "commit");
    ?>

You should not close the connection to the PostgreSQL server before closing the large object.

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