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https://issues.apache.org/jira/browse/HIVE-18454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=17175446#comment-17175446
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Renukaprasad C commented on HIVE-18454:
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[~kgyrtkirk],
I tried to simulate the issue with the provided queries. but i couldnt on
branch - 3.1.0. Is there any specific scenario or it got handled as part of
some other issue already? Thanks in advance.
> Incorrect rownum estimation in joins
>
>
> Key: HIVE-18454
> URL: https://issues.apache.org/jira/browse/HIVE-18454
> Project: Hive
> Issue Type: Sub-task
> Components: Statistics
>Reporter: Zoltan Haindrich
>Priority: Major
>
> row counts seems to be off the charts...sometimes ~12 rows estimated when
> the table has only 10 rows
> {code:java}
> create table s (x int);
> insert into s values
> (1),(2),(3),(4),(5),
> (6),(7),(8),(9),(10);
> create table tu(id_uv int,id_uw int,u int);
> create table tv(id_uv int,v int);
> create table tw(id_uw int,w int);
> from s
> insert overwrite table tu
> select x,x,x
> where x<=6 or x=10
> insert overwrite table tv
> select x,x
> where x<=3 or x=10
> insert overwrite table tw
> select x,x
> ;
> set hive.explain.user=true;
> explain analyze
> select sum(u*v*w) from tu
> join tv on (tu.id_uv=tv.id_uv)
> join tw on (tu.id_uw=tw.id_uw)
> where w>9 and u>1 and v>3;
> desc formatted tv;
> {code}
> explain analyze output:
> {code:java}
> | Plan optimized by CBO. |
> ||
> | Vertex dependency in root stage|
> | Map 1 <- Map 3 (BROADCAST_EDGE), Map 4 (BROADCAST_EDGE) |
> | Reducer 2 <- Map 1 (CUSTOM_SIMPLE_EDGE)|
> ||
> | Stage-0|
> | Fetch Operator |
> | limit:-1 |
> | Stage-1|
> | Reducer 2|
> | File Output Operator [FS_21] |
> | Group By Operator [GBY_19] (rows=1/1 width=8) |
> | Output:["_col0"],aggregations:["sum(VALUE._col0)"] |
> | <-Map 1 [CUSTOM_SIMPLE_EDGE] |
> | PARTITION_ONLY_SHUFFLE [RS_18] |
> | Group By Operator [GBY_17] (rows=1/1 width=8) |
> | Output:["_col0"],aggregations:["sum(_col0)"] |
> | Select Operator [SEL_15] (rows=48400/1 width=5) |
> | Output:["_col0"] |
> | Map Join Operator [MAPJOIN_31] (rows=48400/1 width=5) |
> |
> Conds:MAPJOIN_30._col1=RS_13._col0(Inner),HybridGraceHashJoin:true,Output:["_col2","_col4","_col6"]
> |
> | <-Map 4 [BROADCAST_EDGE] |
> | BROADCAST [RS_13]|
> | PartitionCols:_col0|
> | Select Operator [SEL_8] (rows=3/1 width=3) |
> | Output:["_col0","_col1"] |
> | Filter Operator [FIL_29] (rows=3/1 width=3) |
> | predicate:((w > 9) and id_uw is not null) |
> | TableScan [TS_6] (rows=10/10 width=3) |
> |
> default@tw,tw,Tbl:COMPLETE,Col:NONE,Output:["id_uw","w"] |
> | <-Map Join Operator [MAPJOIN_30] (rows=44000/1 width=5) |
> |
> Conds:SEL_2._col0=RS_10._col0(Inner),HybridGraceHashJoin:true,Output:["_col1","_col2","_col4"]
> |
> | <-Map 3 [BROADCAST_EDGE] |
> | BROADCAST [RS_10] |
> | PartitionCols:_col0 |
> | Select Operator [SEL_5] (rows=1632/1 width=3) |
> | Output:["_col0","_col1"] |
> | Filter Operator [FIL_28] (rows=1632/1 width=3) |
> | predicate:((v > 3) and id_uv is not null) |
> | TableScan [TS_3] (rows=4898/4 width=3) |
> |
> default@tv,tv,Tbl:COMPLETE,Col:NONE,Output:["id_uv","v"] |
> | <-Select Operator [SEL_2] (rows=4/6 width=5) |
> | Output:["_col0","_col1","_col2"] |
> | Filter Operator [FIL_27] (rows=4/6 width=5) |
> | predicate:((u > 1) and id_uv is not null and id_uw
> is not null) |
> | TableScan [TS_0] (rows=12/7 width=5) |
> |
> default@tu,tu,Tbl:COMPLETE,Col:NONE,Output:["id_uv","id_uw","u"] |
> {code}
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