You are viewing a plain text version of this content. The canonical link for it is here.
Posted to issues@kylin.apache.org by "Billy Liu (JIRA)" <ji...@apache.org> on 2018/03/18 18:28:00 UTC
[jira] [Updated] (KYLIN-3149) Calcite's
ReduceExpressionsRule.PROJECT_INSTANCE not working as expected
[ https://issues.apache.org/jira/browse/KYLIN-3149?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Billy Liu updated KYLIN-3149:
-----------------------------
Fix Version/s: v2.4.0
> Calcite's ReduceExpressionsRule.PROJECT_INSTANCE not working as expected
> ------------------------------------------------------------------------
>
> Key: KYLIN-3149
> URL: https://issues.apache.org/jira/browse/KYLIN-3149
> Project: Kylin
> Issue Type: Bug
> Affects Versions: v2.2.0
> Reporter: hongbin ma
> Assignee: yiming.xu
> Priority: Major
> Fix For: v2.4.0
>
> Attachments: dump.txt
>
>
> for queries like:
> {code:sql}
> select TRANS_ID from kylin_sales group by cast (case
> WHEN '1030101' = '1030101' then substring(COALESCE(OPS_USER_ID, '999999999999'), 1, 1)
> when '1030101' = '1030102' then substring(COALESCE(OPS_REGION, '999999999999'), 1, 1)
> when '1030101' = '1030103' then substring(COALESCE(LSTG_FORMAT_NAME, '999999999999'), 1, 1)
> when '1030101' = '1030104' then substring(COALESCE(LSTG_FORMAT_NAME, '999999999999'), 1, 1)
> end as varchar(256)), TRANS_ID;
> {code}
> the expected logical plan after volcano is:
> {code}
> EXECUTION PLAN BEFORE REWRITE
> OLAPToEnumerableConverter
> OLAPProjectRel(TRANS_ID=[$1], ctx=[])
> OLAPLimitRel(ctx=[], fetch=[50000])
> OLAPAggregateRel(group=[{0, 1}], ctx=[])
> OLAPProjectRel($f0=[SUBSTRING(CASE(IS NOT NULL($9), $9, '999999999999'), 1, 1)], TRANS_ID=[$0], ctx=[])
> OLAPTableScan(table=[[DEFAULT, KYLIN_SALES]], ctx=[], fields=[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]])
> {code}
> however the actual is:
> {code}
> EXECUTION PLAN BEFORE REWRITE
> OLAPToEnumerableConverter
> OLAPLimitRel(ctx=[], fetch=[50000])
> OLAPProjectRel(TRANS_ID=[$1], ctx=[])
> OLAPAggregateRel(group=[{0, 1}], ctx=[])
> OLAPProjectRel($f0=[CAST(CASE(=('1030101', '1030101'), SUBSTRING(CASE(IS NOT NULL($9), $9, '999999999999'), 1, 1), =('1030101', '1030102'), SUBSTRING(CASE(IS NOT NULL($10), $10, '999999999999'), 1, 1), =('1030101', '1030103'), SUBSTRING(CASE(IS NOT NULL($2), $2, '999999999999'), 1, 1), =('1030101', '1030104'), SUBSTRING(CASE(IS NOT NULL($2), $2, '999999999999'), 1, 1), null)):VARCHAR(256) CHARACTER SET "UTF-16LE" COLLATE "UTF-16LE$en_US$primary"], TRANS_ID=[$0], ctx=[])
> OLAPTableScan(table=[[DEFAULT, KYLIN_SALES]], ctx=[], fields=[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]])
> {code}
> looks like Calcite's ReduceExpressionsRule.PROJECT_INSTANCE not working as expected. If we dump the internal state of this VolcanoPlanner (org.apache.calcite.plan.volcano.VolcanoPlanner#dump), line 19-21 from the complete dump is attached:
> {code}
> rel#337:Subset#1.OLAP.[], best=rel#339, importance=0.6561
> rel#339:OLAPProjectRel.OLAP.[](input=rel#303:Subset#0.OLAP.[],$f0=CAST(CASE(=('1030101', '1030101'), SUBSTRING(CASE(IS NOT NULL($9), $9, '999999999999'), 1, 1), =('1030101', '1030102'), SUBSTRING(CASE(IS NOT NULL($10), $10, '999999999999'), 1, 1), =('1030101', '1030103'), SUBSTRING(CASE(IS NOT NULL($2), $2, '999999999999'), 1, 1), =('1030101', '1030104'), SUBSTRING(CASE(IS NOT NULL($2), $2, '999999999999'), 1, 1), null)):VARCHAR(256) CHARACTER SET "UTF-16LE" COLLATE "UTF-16LE$en_US$primary",TRANS_ID=$0,ctx=), rowcount=100.0, cumulative cost={15.0 rows, 25.05 cpu, 0.0 io}
> rel#348:OLAPProjectRel.OLAP.[](input=rel#303:Subset#0.OLAP.[],$f0=SUBSTRING(CASE(IS NOT NULL($9), $9, '999999999999'), 1, 1),TRANS_ID=$0,ctx=), rowcount=100.0, cumulative cost={15.0 rows, 25.05 cpu, 0.0 io}
> {code}
> we see two rels with same cost: #339 and #348, where #339 is created from LogicalProject = (OLAPProjectRule)=> OLAPProject, and #348 is created from LogicalProject =( ReduceExpressionsRule) => Reduced LogicalProject =(OLAPProjectRule)=> Reduced OLAPProject . Since ReduceExpressionsRule require Logical Project rather than OLAP Project, #339 is never reduced.
> The worse thing is that cost of #339 and #348 are same. By current volcano planner algorithm the first met rel will be chosen, so unexpected rel is chosen
> A simple approach to fix this is to refine the rel choosing algorithm: when two rels are equal in cost, choose a "simpler" one. Since we don't have a perfect measurement of "simple", we simply choose the rel with smaller toString() length
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)