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rules.sgml
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Tom Lane authored
The example of expansion of multiple views claimed that the resulting subquery nest would not get fully flattened because of an aggregate function. There's no aggregate in the example, though, only a user defined function confusingly named MIN(). In a modern server, the reason for the non-flattening is that MIN() is volatile, but I'm unsure whether that was true back when this text was written. Let's reduce the confusion level by using LEAST() instead (which we didn't have at the time this example was created). And then we can just say that the planner will flatten the sub-queries, so the rewrite system doesn't have to. Noted by Paul Jungwirth. This text is old enough to vote, so back-patch to all supported branches. Discussion: https://postgr.es/m/CA+renyXZFnmp9PcvX1EVR2dR=XG5e6E-AELr8AHCNZ8RYrpnPw@mail.gmail.com
Tom Lane authoredThe example of expansion of multiple views claimed that the resulting subquery nest would not get fully flattened because of an aggregate function. There's no aggregate in the example, though, only a user defined function confusingly named MIN(). In a modern server, the reason for the non-flattening is that MIN() is volatile, but I'm unsure whether that was true back when this text was written. Let's reduce the confusion level by using LEAST() instead (which we didn't have at the time this example was created). And then we can just say that the planner will flatten the sub-queries, so the rewrite system doesn't have to. Noted by Paul Jungwirth. This text is old enough to vote, so back-patch to all supported branches. Discussion: https://postgr.es/m/CA+renyXZFnmp9PcvX1EVR2dR=XG5e6E-AELr8AHCNZ8RYrpnPw@mail.gmail.com
