C++: Fix performance of bbEntryReachesLocally (1.19)#576
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This predicate was fast with the queries and engine from 1.18. With the queries from `master` it got a bad join order in the `UninitializedLocal.ql` query, which made it take 2m34s on Wireshark. This commit decomposes `bbEntryReachesLocally` into two predicates that together take only 4s.
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LGTM, though at this stage I'd definitely like to give it a try before merging... |
geoffw0
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Nov 29, 2018
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I have two wireshark snapshots on my machine. On one of them this speeds it up from 807s to 633s, by making bbEntryReachesLocally disappear from the list of most expensive predicates. The other snapshot apparently hangs around 520s with much less contribution from bbEntryReachesLocally (perhaps it's missing something pathological like a giant test case). In any case this seems to be doing what it promises.
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This predicate was fast with the queries and engine from 1.18. With the queries from
masterit got a bad join order in theUninitializedLocal.qlquery, which made it take 2m34s on Wireshark. This commit decomposesbbEntryReachesLocallyinto two predicates that together take only 4s.