Tom Lane wrote:
So I was looking for other omissions in utility.c, and I noticed that check_xact_readonly() doesn't reject CLUSTER, REINDEX, or VACUUM. Now the notion of "read only" that we're trying to enforce is pretty weak (I think it's effectively "no writes to non-temp tables"). But I can't see that CLUSTER is a read-only operation even under the weakest definitions, and I'm not seeing the rationale for REINDEX or VACUUM here either.
I think the way the SQL standard meant the read-only flag is that the transaction doesn't change the structure of or the data in the database as seen by the next guy. So all of these commands are OK, I think.
A theoretical use case is that you should be able to do the maximum set of useful work in read-only mode on a Slony-I slave. No I haven't checked what Slony does with these three commands, so let me have it. :-)
Other definitions might be OK, but I can't see one offhand that is based on the current behavior but disallows these three commands. "No disk writes" or "no big locks" is probably not what the SQL standard meant.
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