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9b9c5f279e
The behavior of something like ALTER TABLE transactions ADD COLUMN status varchar(30) DEFAULT 'old', ALTER COLUMN status SET default 'current'; is to fill existing table rows with 'old', not 'current'. That's intentional and desirable for a couple of reasons: * It makes the behavior the same whether you merge the sub-commands into one ALTER command or give them separately; * If we applied the new default while filling the table, there would be no way to get the existing behavior in one SQL command. The same reasoning applies in cases that add a column and then manipulate its GENERATED/IDENTITY status in a second sub-command, since the generation expression is really just a kind of default. However, that wasn't very obvious (at least not to me; earlier in the referenced discussion thread I'd thought it was a bug to be fixed). And it certainly wasn't documented. Hence, add documentation, code comments, and a test case to clarify that this behavior is all intentional. In passing, adjust ATExecAddColumn's defaults-related relkind check so that it matches up exactly with ATRewriteTables, instead of being effectively (though not literally) the negated inverse condition. The reasoning can be explained a lot more concisely that way, too (not to mention that the comment now matches the code, which it did not before). Discussion: https://postgr.es/m/10365.1558909428@sss.pgh.pa.us |
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| .. | ||
| aggregatecmds.c | ||
| alter.c | ||
| amcmds.c | ||
| analyze.c | ||
| async.c | ||
| cluster.c | ||
| collationcmds.c | ||
| comment.c | ||
| constraint.c | ||
| conversioncmds.c | ||
| copy.c | ||
| createas.c | ||
| dbcommands.c | ||
| define.c | ||
| discard.c | ||
| dropcmds.c | ||
| event_trigger.c | ||
| explain.c | ||
| extension.c | ||
| foreigncmds.c | ||
| functioncmds.c | ||
| indexcmds.c | ||
| lockcmds.c | ||
| Makefile | ||
| matview.c | ||
| opclasscmds.c | ||
| operatorcmds.c | ||
| policy.c | ||
| portalcmds.c | ||
| prepare.c | ||
| proclang.c | ||
| publicationcmds.c | ||
| schemacmds.c | ||
| seclabel.c | ||
| sequence.c | ||
| statscmds.c | ||
| subscriptioncmds.c | ||
| tablecmds.c | ||
| tablespace.c | ||
| trigger.c | ||
| tsearchcmds.c | ||
| typecmds.c | ||
| user.c | ||
| vacuum.c | ||
| variable.c | ||
| view.c | ||