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    <p>I see four useful ways to replace the contents of the table. None of them is "obviously right", but it depends on your requirements.</p> <ol> <li><p>(In a single transaction) <code>DELETE FROM foo; INSERT INTO foo SELECT ...</code></p> <p><strong>Pro:</strong> Best concurrency: doesn't lock out other transactions accessing the table, as it leverages Postgres's MVCC.</p> <p><strong>Con:</strong> Probably the slowest if you measure the insert-speed alone. Causes autovacuum to clean up dead rows, thus creating a higher I/O load.</p></li> <li><p><code>TRUNCATE foo; INSERT INTO foo SELECT ...</code></p> <p><strong>Pro:</strong> Fastest for smaller tables. Causes less write I/O than #1</p> <p><strong>Con:</strong> Excludes all other readers -- other transactions reading from the table will have to wait.</p></li> <li><p><code>TRUNCATE foo</code>, DROP all indexes on table, <code>INSERT INTO foo SELECT ...</code>, re-create all indexes.</p> <p><strong>Pro:</strong> Fastest for large tables, because creating indexes with <code>CREATE INDEX</code> is faster than updating them incrementally.</p> <p><strong>Con:</strong> Same as #2</p></li> <li><p>The switcheroo. Create two identical tables <code>foo</code> and <code>foo_tmp</code></p> <pre><code>TRUNCATE foo_tmp; INSERT INTO foo_tmp SELECT ...; ALTER TABLE foo RENAME TO foo_tmp1; ALTER TABLE foo_tmp RENAME TO foo; ALTER TABLE foo_tmp1 RENAME TO foo_tmp; </code></pre> <p>Thanks to PostgreSQL's transactional DDL capabilities, if this is done in a transaction, the rename is performed without other transactions noticing. You can also combine this with #3 and drop/create indexes.</p> <p><strong>Pro:</strong> Less I/O performed, like #2, and without locking out other readers (locks taken only during the rename part).</p> <p><strong>Con:</strong> The most complicated. Also you cannot have foreign keys or views pointing to the table, as they would point to the <em>wrong</em> table after renaming it.</p></li> </ol>
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    1. COI had to rename/drop my indexes after doing the combined #4 and #3. Primary-key indexes are renamed automatically, others are not. The total time to drop and rebuild ~800.000 rows from a view went from 90s to about 20s. Thanks for the tip.
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