Description:
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Issues with freeing Prepared Queries
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Here are some issues with freeing prepared queries in the
PostgreSQL implementation of DB.

1) If you use the query member in the form where you provide parameter values as a second argument the query is prepared and executed but the values produced by the prepare step are never freed. This leads to a considerable memory leaks if the query member is used repeatedly in a long-running process.

Here's a suggested fix for this one. In DB_common::query,
changes marked with "CSCS":

    function &query($query, $params = array()) {
        if (sizeof($params) > 0) {
            $sth = $this->prepare($query);
            if (DB::isError($sth)) {
                return $sth;
            }
// CSCS Prepared query should be freed 
// CSCS     return $this->execute($sth, $params);
            $res = &$this->execute($sth, $params); // CSCS
            $this->freeResult($sth);               // CSCS
            return $res;                           // CSCS
        } else {


2) If you explicitly prepare a query there is no documented method defined for freeing the prepared version. This is (generally) a smaller memory leak since queries are usually prepared once and re-used often.

3) The freeResult member of DB_pgsql does not unset the query's entry in the prepared_queries array. The entries in the prepare_tokens and prepare_types arrays are freed.

Suggested fix in DB_pgsql::freeResult is to add one line...

     unset($this->prepare_tokens[(int)$result]);
     unset($this->prepare_types[(int)$result]);
     unset($this->prepared_queries[(int)$result]); // CSCS

4) Not sure what effect this has but the prepare_tokens and prepare_types arrays are defined in both the base DB_common class and the DB_pgsql class. It seems like just having them in the DB_common class would be enough.


Reproduce code:
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Let me know if you would like some reproduce code.