C++: Speed up SuspiciousAddWithSizeof select#3352
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This `select` clause had become very slow after we started caching
`ElementBase::toString` because the query used string concatenation to
produce alert messages, and those string concatenations were done very
early in the pipeline, producing lots of strings that would be discarded
moments later.
By using `$@` to interpolate elements into strings, the concatenation is
done outside of QL.
Testing on a Chromium snapshot, this commit takes us from
#select#ff ................ 6m2s
to
#select#cpe#134#fff ....... 15.2s
MathiasVP
approved these changes
Apr 24, 2020
MathiasVP
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LGTM (assuming the tests pass).
Would it be worthwhile to go through the LGTM suite and check if other queries suffer from the same issue? I suppose this can almost be done with a grep
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I'd prefer not to make queries uglier if they don't have a substantial performance problem. If we can solve https://github.com/github/codeql-c-analysis-team/issues/56 in the libraries and/or optimiser, that seems better than chasing down individual queries. |
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This
selectclause had become very slow after we started cachingElementBase::toStringbecause the query used string concatenation to produce alert messages, and those string concatenations were done very early in the pipeline, producing lots of strings that would be discarded moments later.By using
$@to interpolate elements into strings, the concatenation is done outside of QL.Testing on a Chromium snapshot, this PR takes us from
to