release-26.1: opt/memo: fix exponential behavior when formatting nested UDFs#166131
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yuzefovich merged 1 commit intocockroachdb:release-26.1from Mar 19, 2026
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This commit fixes seemingly exponential behavior when formatting nested UDFs when `ExprFmtHideScalars` flag is not set (which is the case for `EXPLAIN (OPT, TYPES)` and `opt-vv.txt` file of the stmt bundle). This is done by keeping track of "repetitive calls" in addition to already being tracked "recursive calls". Once we've seen a call to a UDF, the UDF's future invocation aren't formatted and are simply replaced with `repetitive-call`. The impact of the old behavior is that it can easily lead to OOMs. For example, running the regression test for issue 161993 via EXPLAIN ANALYZE (DEBUG) on my laptop consumes 50GiB and doesn't finish within 30s. Release note (bug fix): Previously, running `EXPLAIN ANALYZE (DEBUG)` on a query that invokes a UDF with many blocks in some cases could cause OOMs, and this is now fixed.
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Backport 1/1 commits from #166026 on behalf of @yuzefovich.
This commit fixes seemingly exponential behavior when formatting nested UDFs when
ExprFmtHideScalarsflag is not set (which is the case forEXPLAIN (OPT, TYPES)andopt-vv.txtfile of the stmt bundle). This is done by keeping track of "repetitive calls" in addition to already being tracked "recursive calls". Once we've seen a call to a UDF, the UDF's future invocation aren't formatted and are simply replaced withrepetitive-call.The impact of the old behavior is that it can easily lead to OOMs. For example, running the regression test for issue 161993 via EXPLAIN ANALYZE (DEBUG) on my laptop consumes 50GiB and doesn't finish within 30s.
Fixes: #166024.
Release note (bug fix): Previously, running
EXPLAIN ANALYZE (DEBUG)on a query that invokes a UDF with many blocks in some cases could cause OOMs, and this is now fixed.Release justification: low-risk bug fix.