24.03.11 20:41, Merlin Moncure написав(ла):
2011/3/24 Віталій Тимчишин<tivv00@xxxxxxxxx>:
This can se GUC-controllable. Like plan_safety=0..1 with low default value.
This can influence costs of plans where cost changes dramatically with small
table changes and/or statistics is uncertain. Also this can be used as
direct "hint" for such dangerous queries by changing GUC for session/single
query.
ISTM if you add statistics miss and 'risk margin' to the things the
planner would have to consider while generating a plan, you are
greatly increasing the number of plan paths that would have to be
considered for any non trivial query.
Why so? I simply change cost estimation functions. This won't change
number of pathes.
Best regards, Vitalii Tymchyshyn.
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