Vladimir Ozerov created IGNITE-10305:
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Summary: SQL: Optimize query execution if it targets only one or
none partitions
Key: IGNITE-10305
URL: https://issues.apache.org/jira/browse/IGNITE-10305
Project: Ignite
Issue Type: Task
Components: sql
Reporter: Vladimir Ozerov
Fix For: 2.8
This is a part of "Partition Pruning" IEP [1].
Currently we try to extract partitions from map queries and route requests
accordingly. Several problems with this approach:
1) Individual map queries may target the same partition, but we never know
that, so we may want to setup a merge table when it is not really needed.
2) Sometimes query may reduce to no partitions. In this case we should not
execute anything at all and simply return empty result set.
3) If the whole query targets only one partition, we may skip the whole
splitter phase!
I propose to do the following:
# Try to extract partition from "original" query.
# If we see that exactly one partition is involved, then original query is a
map query, and reduce should be performed in "skip merge table" mode
# If we see that there are no partitions because query is invalid (e.g. {{id =
1 AND id = 2}}), then stop and return no results. This decision should be
cached in two-step plan.
# If we see that there are some partitions, then we should apply arguments and
see the result. If result set is empty - return, but do not cache empty result
set decision, as it may change for another set of arguments.
# If none of above hold, then do pushdowns and split, and analyze partitions of
individual map queries. For those of them where partition set is empty, we
should return empty result set without executing anything.
[1]
https://cwiki.apache.org/confluence/display/IGNITE/IEP-24%3A+SQL+Partition+Pruning
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