Maybe the best solution is to abandon the ALTER TABLE approach entirely, and instead invent a new set of commands
CREATE STATISTICS DROP STATISTICS
(ALTER STATISTICS seems a bit excessive at this point).
Another thing is that perhaps we should add names for statistics, just like we do for constraints, for example. Otherwise the DROP STATISTICS handling is rather awkward - for example if the user creates stats twice by mistake, he's unable to drop just one of them.
Do you think this modified syntax makes sense? I'll have time to hack on this over the next few days.
Koyotaro's changes to force COLUMN to be required won't get through.
ISTM that we could use COLLECT STATISTICS instead of ADD STATISTICS, and use REMOVE STATISTICS instead of DROP STATISTICS. That way we can use ALTER TABLE rather than inventing a new command. 5 minute change...
Unless there is some better reason for a whole new command?
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Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services