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https://issues.apache.org/jira/browse/CALCITE-830?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde updated CALCITE-830:
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Summary: Keep VolcanoPlanner state consistent when stats are non-monotonic
(was: VolcanoPlanner may have inconsistent state and may not pick the cheapest
plan if stats (e.g. row count) is not monotonic increasing with cost)
> Keep VolcanoPlanner state consistent when stats are non-monotonic
> -----------------------------------------------------------------
>
> Key: CALCITE-830
> URL: https://issues.apache.org/jira/browse/CALCITE-830
> Project: Calcite
> Issue Type: Bug
> Reporter: Maryann Xue
> Assignee: Julian Hyde
> Fix For: 1.5.0
>
> Attachments: CALCITE-830.patch, calcite.log.2
>
>
> VolcanoPlanner may have inconsistent state and may not pick the cheapest plan
> if stats (e.g. row count) is not monotonic increasing with cost.
> An example can be:
> select i.item_id, o.quantity from orderTable o join (select distinct item_id
> from itemTable) i on o.item_id = i.item_id
> where item_id is the primary key of itemTable and thus is unique (distinct).
> The AggregateRemoveRule will be applied for the subquery "select distinct
> item_id from itemTable", and generates a cheaper sub-tree equivalent to
> "select item_id from itemTable". However the original Rel sub-tree gives a
> smaller rowCount (it shouldn't have, but let's say it's an independent issue)
> than the new Rel sub-tree (after applying AggregateRemoveRule). By picking
> the new Rel sub-tree as the new best of the child subset, the parent RelNode
> "Join" now has a higher cost, but this change is not reflected in its own
> enclosing subset, which then causes inconsistency.
> Please see the attached log:
> line 27099 ~ 27100:
> {code}
> rel#221:Subset#5.PHOENIX_CLIENT.[0], best=rel#220,
> importance=0.4984472052723946
>
> rel#220:PhoenixToClientConverter.PHOENIX_CLIENT.[0](input=rel#50:Subset#5.PHOENIX_SERVERJOIN.[0]),
> rowcount=525.0, cumulative cost={153.3897966465855 rows, 6 2.0 cpu, 0.0
> io}
> {code}
> line 27092 ~ 27093:
> {code}
> rel#50:Subset#5.PHOENIX_SERVERJOIN.[0], best=rel#49,
> importance=0.4984472052723946
>
> rel#49:PhoenixServerJoin.PHOENIX_SERVERJOIN.[[0]](left=rel#47:Subset#1.PHOENIX_SERVER.[0],right=rel#48:Subset#4.PHOENIX_CLIENT.[],condition==($1,
> $3),joinTyp e=inner), rowcount=525.0, cumulative
> cost={193.63272822430963 rows, 62.0 cpu, 0.0 io}
> {code}
> rel#220 has a lower cumulative cost than its input rel#50.
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