將PHP Session存在Postgres數據庫后端

一個開發環境有多個網站，需要使用不同的session，解決方案很多。不過這次也高大上一把，用數據庫存，方便以后擴展。

首先是數據庫的部分

--drop table php_session
create unlogged table php_session
(
    sess_id varchar(32) primary key,
    modify_time timestamp with time zone not null,
    sess_data varchar(3000) default ''
);

create index concurrently idx_php_session_modify_time on php_session(modify_time);

--set_session(id, data)
create or replace function set_session(varchar, varchar) returns void as $set_session$
    with upsert as (
        update php_session
        set modify_time = current_timestamp, sess_data = $2
        where sess_id = $1
        returning 1
    )
    insert into php_session (sess_id, modify_time, sess_data)
    select $1, current_timestamp, $2
    where not exists (
        select 1 from upsert
    );
$set_session$ language sql;

--get_session(id)
create or replace function get_session(varchar) returns varchar as $get_session$
    select sess_data from php_session where sess_id = $1
$get_session$ language sql;

--del_session
create or replace function del_session(varchar) returns void as $del_session$
    delete from php_session where sess_id = $1
$del_session$ language sql;

--gc_session
create or replace function gc_session() returns void as $del_session$
    delete from php_session where modify_time < current_timestamp - interval '30 days'
$del_session$ language sql;

然后是PHP的部分

<?php

session_set_save_handler(
    function ($savePath, $sessionName) {//open
        return true;
    },
    function () {//close
        return true;
    },
    function ($id) {//read
        $sql = "select get_session($1)";
        $stmt = pg_query_params(SESSION_CONN, $sql, array($id));
        $result = pg_fetch_row($stmt);

        return $result[0];
    },
    function ($id, $data) {//write
        $sql = "select set_session($1, $2)";
        pg_query_params(SESSION_CONN, $sql, array($id, $data));
        return true;
    },
    function ($id) {//destroy
        $sql = "select del_session($1)";
        pg_query_params(SESSION_CONN, $sql, array($id, $data));
        return true;
    },
    function ($maxlifetime) {//gc
        //php needn't control the global session gc 
        return true;
    }
);

register_shutdown_function('session_write_close');

?>

然后只要在session_start之前調用這個就可以了

至于SESSION_CONN，那是我定義的一個常量，表示一個指向session數據庫的鏈接而.

來自：http://my.oschina.net/visualgui823/blog/290074