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copied!<p>Erwin nails it, but let me add that the extended query protocol allows you to use more flavors of prepared statements. Besides avoiding re-parsing and re-planning, one big advantage of prepared statements is to send parameter values separately, which avoids escaping and parsing overhead, not to mention the opportunity for SQL injections and bugs if you don't use an API that handles parameters in a manner you can't forget to escape them.</p> <p><a href="http://www.postgresql.org/docs/9.1/static/protocol-flow.html" rel="nofollow">http://www.postgresql.org/docs/9.1/static/protocol-flow.html</a></p> <blockquote> <p>Query planning for named prepared-statement objects occurs when the Parse message is processed. If a query will be repeatedly executed with different parameters, it might be beneficial to send a single Parse message containing a parameterized query, followed by multiple Bind and Execute messages. This will avoid replanning the query on each execution.</p> <p>The unnamed prepared statement is likewise planned during Parse processing if the Parse message defines no parameters. But if there are parameters, query planning occurs every time Bind parameters are supplied. This allows the planner to make use of the actual values of the parameters provided by each Bind message, rather than use generic estimates.</p> </blockquote> <p>So, if your DB interface supports it, you can use unnamed prepared statements. It's a bit of a middle ground between a query and a usual prepared statement.</p> <p>If you use PHP with PDO, please note that PDO's prepared statement implementation is rather useless for postgres, since it uses named prepared statements, but re-prepares every time you call prepare(), no plan caching takes place. So you get the worst of both : many roundtrips and plan without parameters. I've seen it be 1000x slower than pg_query() and pg_query_params() on specific queries where the postgres optimizer really needs to know the parameters to produce the optimal plan. pg_query uses raw queries, pg_query_params uses unnamed prepared statements. Usually one is faster than the other, that depends on the size of parameter data.</p>

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