main: update optgen Op alias to match current memo group member #94112
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The generated code looks like this with the fix: // [GenerateStreamingGroupByLimitOrderingHint]
{
_partlyExplored := _rootOrd < _rootState.start
aggregation := _root.Input
_state := _e.lookupExploreState(aggregation)
if !_state.fullyExplored {
_fullyExplored = false
}
var _member memo.RelExpr
for _ord := 0; _ord < _state.end; _ord++ {
if _member == nil {
_member = aggregation.FirstExpr()
} else {
_member = _member.NextExpr()
}
aggregation = _member
if !_partlyExplored || _ord >= _state.start {
if _member.Op() == opt.GroupByOp || _member.Op() == opt.DistinctOnOp {
...
... |
DrewKimball
approved these changes
Dec 21, 2022
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Reviewable status:
complete! 1 of 0 LGTMs obtained
Fixes cockroachdb#94042 This fixes a slightly confusing feature of optgen where an alias in a match rule is assigned to the first expression in the group, and may be of a different expression type than the allowed Ops in the match rule. Example: ``` [GenerateStreamingGroupByLimitOrderingHint, Explore] (Limit $aggregation:(GroupBy | DistinctOn ``` Given this match rule, it looks like `$aggregation` can only be a GroupBy or DistinctOn expression. But in cockroachdb#94042, it is sometimes a Select expression. The variable is later used to generate a new expression with the assumption it is one of the allowed Op types, causing a panic. This is fixed by updating the optgen rule gen code to keep the alias up-to-date with the current memo group member being examined in the match rule, as it cycles through all members in the group. Release note: None
msirek
commented
Dec 22, 2022
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TFTR!
bors r=DrewKimball
Reviewable status:
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Build succeeded: |
This was referenced Dec 22, 2022
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Fixes #94042
This fixes a slightly confusing feature of optgen where an alias in a match rule is assigned to the first expression in the group, and may be of a different expression type than the allowed Ops in the match rule.
Example:
Given this match rule snippet, it looks like
$aggregationcan only be a GroupBy or DistinctOn expression. But in #94042, it is sometimes a Select expression. The variable is later used to generate a new expression with the assumption it is one of the allowed Op types, causing a panic.This is fixed by updating the optgen rule gen code to keep the alias up-to-date with the current memo group member being examined in the match rule, as it cycles through all members in the group.
Release note: None