網路上找來找去……
沒看到有人寫相關的解法….
加上不想用mysql-proxy來解這部份…

所以打算從code 的部份下手
看到最後只能動Zend Framework 的code 了(還沒想到可以不動ZF 的code 而做到DB LB的方法)

我是先從function save 下手去找..

Zend/Table/Row/Abstract.php:    public function save()

public function save()
    {
        /**
         * If the _cleanData array is empty,
         * this is an INSERT of a new row.
         * Otherwise it is an UPDATE.
         */
        if (empty($this->_cleanData)) {
            return $this->_doInsert();
        } else {
            return $this->_doUpdate();
        }
    }

ZF會自已做update or insert 的區分

再看

/**
     * @return mixed The primary key value(s), as an associative array if the
     *     key is compound, or a scalar if the key is single-column.
     */
    protected function _doInsert()
    {
        /**
         * A read-only row cannot be saved.
         */
        if ($this->_readOnly === true) {
            require_once 'Zend/Db/Table/Row/Exception.php';
            throw new Zend_Db_Table_Row_Exception('This row has been marked read-only');
        }

        /**
         * Run pre-INSERT logic
         */
        $this->_insert();

        /**
         * Execute the INSERT (this may throw an exception)
         */
        $data = array_intersect_key($this->_data, $this->_modifiedFields);
        $primaryKey = $this->_getTable()->insert($data);

        /**
         * Normalize the result to an array indexed by primary key column(s).
         * The table insert() method may return a scalar.
         */
        if (is_array($primaryKey)) {
            $newPrimaryKey = $primaryKey;
        } else {
            $newPrimaryKey = array(current((array) $this->_primary) => $primaryKey);
        }

        /**
         * Save the new primary key value in _data.  The primary key may have
         * been generated by a sequence or auto-increment mechanism, and this
         * merge should be done before the _postInsert() method is run, so the
         * new values are available for logging, etc.
         */
        $this->_data = array_merge($this->_data, $newPrimaryKey);

        /**
         * Run post-INSERT logic
         */
        $this->_postInsert();

        /**
         * Update the _cleanData to reflect that the data has been inserted.
         */
        $this->_refresh();

        return $primaryKey;
    }

$primaryKey = $this->_getTable()->insert($data);

程式在
Zend/Adapter/Abstract.php
這邊有
function update()
function insert()

來看

public function insert($table, array $bind)
    {
        // extract and quote col names from the array keys
        $cols = array();
        $vals = array();
        foreach ($bind as $col => $val) {
            $cols[] = $this->quoteIdentifier($col, true);
            if ($val instanceof Zend_Db_Expr) {
                $vals[] = $val->__toString();
                unset($bind[$col]);
            } else {
                $vals[] = '?';
            }
        }

        // build the statement
        $sql = "INSERT INTO "
             . $this->quoteIdentifier($table, true)
             . ' (' . implode(', ', $cols) . ') '
             . 'VALUES (' . implode(', ', $vals) . ')';

        // execute the statement and return the number of affected rows
        $stmt = $this->query($sql, array_values($bind));
        $result = $stmt->rowCount();
        return $result;
    }

不管insert or update
都是透過query 這個method 去執行sql

所以就在這邊下手吧

public function query($sql, $bind = array())
    {
        // connect to the database if needed
        if ($sql instanceof Zend_Db_Select) {
            if (preg_match('/UPDATE|INSERT|REPLACE/i',$sql->__toString())) {
                $this->closeConnection();
                $this->_config['dbname'] = 'DB_WRITE';
            }
        } else {
            if (preg_match('/UPDATE|INSERT|REPLACE/i',$sql)) {
                $this->closeConnection();
                $this->_config['dbname'] = 'DB_WRITE';
            }
        }
        $this->_connect();

        // is the $sql a Zend_Db_Select object?
        if ($sql instanceof Zend_Db_Select) {
            $sql = $sql->assemble();
        }

        // make sure $bind to an array;
        // don't use (array) typecasting because
        // because $bind may be a Zend_Db_Expr object
        if (!is_array($bind)) {
            $bind = array($bind);
        }

        // prepare and execute the statement with profiling
        $stmt = $this->prepare($sql);
        $stmt->execute($bind);
        // return the results embedded in the prepared statement object
        $stmt->setFetchMode($this->_fetchMode);

        if ($sql instanceof Zend_Db_Select) {
            if (preg_match('/UPDATE|INSERT|REPLACE/i',$sql->__toString())) {
                $this->closeConnection();
                $this->_config['dbname'] = 'DB_READ';
                $this->_connect();
            }
        } else {
            if (preg_match('/UPDATE|INSERT|REPLACE/i',$sql)) {
                $this->closeConnection();
                $this->_config['dbname'] = 'DB_READ';
                $this->_connect();
            }
        }
        return $stmt;
    }

就是很簡單的去parse $sql 是否有UPDATE,INSERT,REPLACE 之類的寫入語法
若有的話就改config

基本上就是這樣…

如果有人有更好的做法…
拜拖 指教一下小第………..
實在是不想弄到ZF 裡面的code 來達到DB LB的功能..