Parallelize iterators #6585
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Parallelize iterators #6585
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Overview
This pull request adds parallel execution of aggregate
SELECTstatements. Iterators within each shard are split using theNewParallelMergeIterator()function which processes iterator batches based on the number of logical cores on the system./cc @jwilder @toddboom
Results
On an AWS
c4.8xlargemachine, performance of a simpleCOUNT()query over 1B points and 100K series drops from1m57sto16.8s. The execution of the count itself is significantly improved, however, the bottleneck on the query is now in the single-threaded planning phase for the 100K series. Parallelizing the planning phase should improve performance significantly for large numbers of series.TODO