frontend: update query pruning #10026
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The current method of excluding/including sub query results in PromQL by comparing to -Inf or +Inf is no longer valid after prometheus/prometheus#15245 due to comparison of native histograms to a float with < or > result in Jeanette's warning, not empty set. To ease migrating to the correct version, I'm not removing the old prune code yet, just adding the new method. The new method uses logical AND operation to intersect the sub query with either a const vector() or an empty vector(). E.g. subquery and on() (vector(1)==1) subquery and on() (vector(-1)==1) which become: subquery (vector(-1)==1) Signed-off-by: György Krajcsovits <[email protected]>
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| { | ||
| // "and on()" is not on top level, "or" has lower precedence. | ||
| `(avg(rate(foo[1m]))) and on() (vector(0) == 1) or avg(rate(bar[1m]))`, | ||
| `(vector(0) == 1) or avg(rate(bar[1m]))`, |
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Couldn't we simplify this further, to avg(rate(bar[1m]))?
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That's more complicated. The main point is to avoid loading chunks and (vector(0)==1) doesn't load chunks, so should be very efficient.
We can add that logic in a new PR, seems to be independent from this optimization, wdyt?
But having two algorithms raises the question of whether they need to be run repeatedly to optimize away everything, so it gets even more complicated.
| { | ||
| // "and on()" is not on top level, due to left-right associativity. | ||
| `(avg(rate(foo[1m]))) and on() (vector(0) == 1) and avg(rate(bar[1m]))`, | ||
| `(vector(0) == 1) and avg(rate(bar[1m]))`, |
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Couldn't we simplify this further, to vector(0) == 1?
| }, | ||
| { // The const expression is on the wrong side. | ||
| `(vector(0) == 1) and on() (avg(rate(foo[1m])))`, | ||
| `(vector(0) == 1) and on() (avg(rate(foo[1m])))`, |
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Same as below - I think this can be simplified to vector(0) == 1.
| }, | ||
| { // Matching on labels. | ||
| `(avg(rate(foo[1m]))) and on(id) (vector(0) == 1)`, | ||
| `(avg(rate(foo[1m]))) and on(id) (vector(0) == 1)`, |
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Couldn't this be simplified to vector(0) == 1? The right side will never produce a result, so we'll never return anything from the left side.
| }, | ||
| { // Not "on" expression. | ||
| `(avg(rate(foo[1m]))) and ignoring() (vector(0) == 1)`, | ||
| `(avg(rate(foo[1m]))) and ignoring() (vector(0) == 1)`, |
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Same as above - the right side will never produce a result.
What this PR does
The current method of excluding/including sub query results in PromQL by comparing to -Inf or +Inf is no longer valid after prometheus/prometheus#15245 due to comparison of native histograms to a float with < or > result in Jeanette's warning, not empty set.
To ease migration away from the old wrong logic, I'm adding the new logic first.
The new method uses logical AND operation to intersect the sub query with either a const vector() or an empty vector(). E.g.
which become:
Which issue(s) this PR fixes or relates to
Fixes N/A
Checklist
CHANGELOG.mdupdated - the order of entries should be[CHANGE],[FEATURE],[ENHANCEMENT],[BUGFIX].about-versioning.mdupdated with experimental features.