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    <p>You can rewrite your procedural logic with <strong>pure SQL</strong> in a <em>single</em> SQL statement using <a href="http://www.postgresql.org/docs/current/interactive/queries-with.html#QUERIES-WITH-MODIFYING" rel="nofollow noreferrer">data-modifying CTEs</a>.</p> <pre><code>WITH usr1 AS (SELECT id FROM users WHERE mongoid = $1) , usr2 AS ( INSERT INTO users (mongoid, shopid, idinshop, attributes) SELECT $1, $2, $3, $4 WHERE NOT EXISTS (SELECT 1 FROM usr1) RETURNING id ) , ses1 AS (SELECT id FROM sessions WHERE mongoid = $5) , ses2 AS ( INSERT INTO sessions (mongoid, shopid, userid, session, traffic, counts) SELECT $5, $2, (SELECT id FROM usr1 NATURAL FULL OUTER JOIN usr2 , $6, $7, $8 WHERE NOT EXISTS (SELECT 1 FROM ses1) RETURNING id ) INSERT INTO events (shopid, sessionid, userid, type, attributes, mongoid) VALUES ($2 , (SELECT id FROM usr1 NATURAL FULL OUTER JOIN usr2) , (SELECT id FROM ses1 NATURAL FULL OUTER JOIN ses2) , $9, $10, $11); </code></pre> <p>Requires Postgres <strong>9.1</strong> or later.<br> Untested. Provide a test case in your question if you want tested answers.</p> <p>Should be considerably faster than individual commands (<a href="https://stackoverflow.com/questions/7510092/which-is-better-performing-calculations-in-sql-or-in-your-application/7518619#7518619">let alone repeated round trips to the db server!</a>).</p> <p>Be aware of <strong>potential concurrency issues</strong> with heavy concurrent load. The single statement presented is already <em>much</em> less likely to cause trouble. But the possibility is there. Possible solutions include <a href="http://www.postgresql.org/docs/current/interactive/explicit-locking.html#LOCKING-TABLES" rel="nofollow noreferrer">manual locking</a> (expensive) <a href="http://www.postgresql.org/docs/current/interactive/explicit-locking.html#ADVISORY-LOCKS" rel="nofollow noreferrer">advisory locks</a> or <a href="http://www.postgresql.org/docs/current/interactive/applevel-consistency.html#SERIALIZABLE-CONSISTENCY" rel="nofollow noreferrer">serializable transactions</a> (may be expensive, too).</p> <p>Related answer with more information:<br> <a href="https://stackoverflow.com/questions/11890599/postgresql-batch-insert-or-ignore/11892007#11892007">Postgresql batch insert or ignore</a></p>
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    1. POHow to use query result in next query inside Postgres transaction?
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    1. USErwin Brandstetter
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    1. POHow to use query result in next query inside Postgres transaction?
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    1. COthanks, seems to be very close. I do get this error: PHP Warning: pg_query_params(): Query failed: ERROR: INSERT has more target columns than expressions LINE 4: INSERT INTO users (mongoid, shopid, idinshop, attri... ^ HINT: The insertion source is a row expression containing the same number of columns expected by the INSERT. Did you accidentally use extra parentheses?
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    2. COI removed parenthesis from INSERT INTO .... SELECT and it works. Thanks! You saved me 4 hours !
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    3. CO@AlexandruRada: Right, amended. I forgot to remove parens after switching from `VALUES` to `SELECT`. Also note the chapter about concurrency I added.
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