[fix](load) fix priority queue order in memtable memory limiter #41278
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kaijchen
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Oct 21, 2024
…he#41278) ## Proposed changes apache#41018 used priority queue when selecting memtables to flush. But the compare function is wrong and causing the order to be the opposite. > Note that the Compare parameter is defined such that it returns true if its first argument comes before its second argument in a weak ordering. But because the priority queue outputs largest elements first, the elements that "come before" are actually output last. That is, the front of the queue contains the "last" element according to the weak ordering imposed by Compare. This PR fixes the compare function to make larger memtables come front.
kaijchen
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Nov 18, 2024
…he#41278) ## Proposed changes apache#41018 used priority queue when selecting memtables to flush. But the compare function is wrong and causing the order to be the opposite. > Note that the Compare parameter is defined such that it returns true if its first argument comes before its second argument in a weak ordering. But because the priority queue outputs largest elements first, the elements that "come before" are actually output last. That is, the front of the queue contains the "last" element according to the weak ordering imposed by Compare. This PR fixes the compare function to make larger memtables come front.
kaijchen
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Nov 18, 2024
…he#41278) ## Proposed changes apache#41018 used priority queue when selecting memtables to flush. But the compare function is wrong and causing the order to be the opposite. > Note that the Compare parameter is defined such that it returns true if its first argument comes before its second argument in a weak ordering. But because the priority queue outputs largest elements first, the elements that "come before" are actually output last. That is, the front of the queue contains the "last" element according to the weak ordering imposed by Compare. This PR fixes the compare function to make larger memtables come front.
kaijchen
added a commit
to kaijchen/doris
that referenced
this pull request
Nov 18, 2024
…he#41278) ## Proposed changes apache#41018 used priority queue when selecting memtables to flush. But the compare function is wrong and causing the order to be the opposite. > Note that the Compare parameter is defined such that it returns true if its first argument comes before its second argument in a weak ordering. But because the priority queue outputs largest elements first, the elements that "come before" are actually output last. That is, the front of the queue contains the "last" element according to the weak ordering imposed by Compare. This PR fixes the compare function to make larger memtables come front.
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Proposed changes
#41018 used priority queue when selecting memtables to flush.
But the compare function is wrong and causing the order to be the opposite.
This PR fixes the compare function to make larger memtables come front.