Dear Postgresql experts,
Looking at vmstat output on my database server I have been suprised to see lots of disk writes going on while it is doing what should be exclusively read-only transactions. I see almost no disk reads as the database concerned is small enough to fit into the OS disk cache.
I suspect that it might be something to do with temporary tables. There are a couple of places where I create temporary tables to "optimise" queries by factoring out what would otherwise be duplicate work. The amount of data being written is of the right order of magnitude for this to be the cause. I fear that perhaps Postgresql is flushing these tables to disk, even though they will be dropped before the end of the transaction. Is this a possibility? What issues should I be aware of with temporary tables? Are there any other common causes of lots of disk writes within read-only transactions? Is there any debug output that I can look at to track this down?
Thanks in advance for any help that you can offer.
Regards,
Phil Endecott.
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