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Revision 11033

Added by Aaron Marcuse-Kubitza over 11 years ago

lib/sql_io.py: put_table(): added link to new INSERT ON DUPLICATE SELECT wiki page, which now contains the explanation in the doc comment

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lib/sql_io.py
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    Note that much of the complexity of the normalizing algorithm is due to
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    PostgreSQL (and other DB systems) not having a native command for
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    insert/on duplicate select. This operation is a cross between MySQL's
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    INSERT ON DUPLICATE KEY UPDATE (which does not provide SELECT
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    functionality), and PostgreSQL's INSERT RETURNING (which throws an error
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    on duplicate instead of returning the existing row).
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    However, PostgreSQL 9.1+ now provides a way to implement insert/on duplicate
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    select just once for each table using the new INSTEAD OF triggers
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    (http://www.postgresql.org/docs/9.1/static/plpgsql-trigger.html),
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    which even support INSERT RETURNING. INSTEAD OF triggers can also be used to
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    implement SQL functions without requiring special support by put_table().
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    (INSTEAD OF triggers were not used when put_table() was developed, because
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    it was necessary to support PostgreSQL 9.0.)
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    INSERT ON DUPLICATE SELECT (wiki.vegpath.org/INSERT_ON_DUPLICATE_SELECT).
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    For PostgreSQL 9.1+, this can now be emulated using INSTEAD OF triggers.
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    For earlier versions, you instead have to use this function.
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    @param in_tables The main input table to select from, followed by a list of
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        tables to join with it using the main input table's pkey

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