Thank you.
them immediately reconstruct 90% of the histograms. I basically hit a bug
Post by Noveljic Nenad«I`m starting to think that actually the best method is to have them
disabled since the beginning and where is the case create one. (instead of
taking Maria`s advise to use auto and evaluate where they create issues) -
not to mention that because of histograms for some tables the incremental
stats don't work as expected â
Disabling histograms at the outset and then enabling them explicitly as
needed might actually work well.
METHOD_OPT AUTO defeats the purpose of incremental stats, as synopses have
to be recreated whenever the statistic gather procedure decides to create
https://nenadnoveljic.com/blog/incremental-statistics-histogram-pitfall/
Best regards,
Nenad
Behalf Of *Laurentiu Oprea
*Sent:* Donnerstag, 18. MÀrz 2021 12:10
*Subject:* Re: disable histogram usage at session / statement level
Thanks a lot, yes both methods work fine .
As a background for my question: I noticed that for a lot of tables the
stats job computed hybrid histograms on ID or PARENT_ID columns and the
cardinality estimate for joins using these columns are orders of
magnitude trillion of rows. Dropping/disabling the histogram resolves the
estimate to 20-30 millions (the expected cardinality)
Because there are so many tables I need to take now query by query and do
a quick evaluation with/without histograms and drop where I see a negative
impact.
I`m starting to think that actually the best method is to have them
disabled since the beginning and where is the case create one. (instead of
taking Maria`s advise to use auto and evaluate where they create issues) -
not to mention that because of histograms for some tables the incremental
stats don't work as expected
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