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# LXXXVIII.PostgreSQL Functions

# 介紹

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, transactions, referential integrity, stored procedures and type extensibility. PostgreSQL is an open source descendant of this original Berkeley code.

# 需求

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/ and http://techdocs.postgresql.org/.

# 安裝

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

# 執行時期組態

`php.ini`中的設定會影響這些函數的行為。

表格 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().

這裡為簡短的結構指令說明。

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.

pgsql.auto_reset_persistent integer

  Detect broken persistent links with pg_pconnect(). Needs a little overhead.

pgsql.ignore_notice integer

  Whether or not to ignore PostgreSQL backend notices.

pgsql.log_notice integer

  Whether or not to log PostgreSQL backends notice messages. The PHP directive pgsql.ignore_notice must be off in order to log notice messages.

# How to use and hints

切記!
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.

切記!
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. 表格 2.Function names changed
Old name | New name
--- | ---
pg_cmdtuples() | pg_affected_rows()
pg_errormessage() | pg_last_error()
pg_exec() | pg_query()
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_getlastoid() | pg_last_oid()
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()
pg_numrows() | pg_num_rows()
pg_numfields() | pg_num_fields()
pg_result() | pg_fetch_result()
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 do not use an older libpq than the PostgreSQL Server to which you will be connecting. 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 its meaning is: "listen on TCP/IP sockets as well as Unix domain sockets".

表格 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.

示範 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

> 備注: PostgreSQL automatically folds all identifiers (e.g. table/column names) to lower-case values. To get it to recognize upper-case values, you must always wrap the identifier in quotes.

# 預先定義常數

以下的常數由此延伸定義，只在這個延伸被編譯成PHP或實行時期被動態載入時有效。

`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)

# 範例

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.

示範 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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