Marios Trivyzas fdac9e99fa
SQL: Fix unecessary evaluation for CASE/IIF (#57159) (#57262)
Previously, `CASE` and `IIF` when translated to painless scripts
(used in GROUP BY, HAVING, WHERE) a custom `caseFunction`
registered in the `InternalSqlScriptUtils` was used. This function
received and array of arbitrary length:
```[condition1, result1, condition2, result2, ... elseResult]```

Painless doesn't know of the context and therefore is evaluating
all conditions and results before invoking the `caseFunction` on them.
As a consequence, erroneous result expressions (i.e. division by 0)
where always evaluated despite of the guarding condition.

Replace the `caseFunction` with painless `<cond> ? <res1> : <res2>`
expressions to properly guard the result expressions and only evaluate
the one for which its guarding condition evaluates to true (or of course
the elseResult).

As a bonus, this approach includes performance benefits since we avoid
unnecessary evaluations of both conditions and result expressions.

Fixes: #49672
(cherry picked from commit 9584b345d89f797bfb658212b928b9812804f02f)
2020-05-28 11:30:14 +02:00
..

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