Volodymyr Vysotskyi created DRILL-6553:
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Summary: Fix TopN for unnest operator
Key: DRILL-6553
URL: https://issues.apache.org/jira/browse/DRILL-6553
Project: Apache Drill
Issue Type: Bug
Reporter: Volodymyr Vysotskyi
Assignee: Volodymyr Vysotskyi
Fix For: 1.14.0
Plan for the query with unnest is chosen non-optimally:
{code:sql}
select customer.c_custkey, customer.c_name, t.o.o_orderkey,t.o.o_totalprice
from dfs.`lateraljoin/multipleFiles` customer,
unnest(customer.c_orders) t(o)
order by customer.c_custkey, t.o.o_orderkey, t.o.o_totalprice
limit 50
{code}
Plan:
{noformat}
00-00 Screen
00-01 ProjectAllowDup(c_custkey=[$0], c_name=[$1], EXPR$2=[$2],
EXPR$3=[$3])
00-02 SelectionVectorRemover
00-03 Limit(fetch=[50])
00-04 SelectionVectorRemover
00-05 Sort(sort0=[$0], sort1=[$2], sort2=[$3], dir0=[ASC],
dir1=[ASC], dir2=[ASC])
00-06 Project(c_custkey=[$2], c_name=[$3], EXPR$2=[ITEM($4,
'o_orderkey')], EXPR$3=[ITEM($4, 'o_totalprice')])
00-07 LateralJoin(correlation=[$cor0], joinType=[inner],
requiredColumns=[{1}])
00-09 Project(T0¦¦**=[$0], c_orders=[$1], c_custkey=[$2],
c_name=[$3])
00-11 Scan(groupscan=[EasyGroupScan
[selectionRoot=file:/home/mapr/drill/exec/java-exec/target/org.apache.drill.exec.physical.impl.lateraljoin.TestE2EUnnestAndLateral/root/lateraljoin/multipleFiles,
numFiles=2, columns=[`**`],
files=[file:/home/mapr/drill/exec/java-exec/target/org.apache.drill.exec.physical.impl.lateraljoin.TestE2EUnnestAndLateral/root/lateraljoin/multipleFiles/cust_order_10_2.json,
file:/home/mapr/drill/exec/java-exec/target/org.apache.drill.exec.physical.impl.lateraljoin.TestE2EUnnestAndLateral/root/lateraljoin/multipleFiles/cust_order_10_1.json]]])
00-08 Project(c_orders0=[$0])
00-10 Unnest [srcOp=00-07]
{noformat}
A similar query, but with flatten:
{code:sql}
select f.c_custkey, f.c_name, f.o.o_orderkey, f.o.o_totalprice from (select
c_custkey, c_name, flatten(c_orders) as o from dfs.`lateraljoin/multipleFiles`
customer) f order by f.c_custkey, f.o.o_orderkey, f.o.o_totalprice limit 50
{code}
has plan:
{noformat}
00-00 Screen
00-01 Project(c_custkey=[$0], c_name=[$1], EXPR$2=[$2], EXPR$3=[$3])
00-02 SelectionVectorRemover
00-03 Limit(fetch=[50])
00-04 SelectionVectorRemover
00-05 TopN(limit=[50])
00-06 Project(c_custkey=[$0], c_name=[$1], EXPR$2=[ITEM($2,
'o_orderkey')], EXPR$3=[ITEM($2, 'o_totalprice')])
00-07 Flatten(flattenField=[$2])
00-08 Project(c_custkey=[$0], c_name=[$1], o=[$2])
00-09 Scan(groupscan=[EasyGroupScan
[selectionRoot=file:/home/mapr/drill/exec/java-exec/target/org.apache.drill.exec.physical.impl.lateraljoin.TestE2EUnnestAndLateral/root/lateraljoin/multipleFiles,
numFiles=2, columns=[`c_custkey`, `c_name`, `c_orders`],
files=[file:/home/mapr/drill/exec/java-exec/target/org.apache.drill.exec.physical.impl.lateraljoin.TestE2EUnnestAndLateral/root/lateraljoin/multipleFiles/cust_order_10_2.json,
file:/home/mapr/drill/exec/java-exec/target/org.apache.drill.exec.physical.impl.lateraljoin.TestE2EUnnestAndLateral/root/lateraljoin/multipleFiles/cust_order_10_1.json]]])
{noformat}
The main difference is that for the case of unnest, a project wasn't pushed to
the scan and Limit with Sort weren't converted to TopN.
The first problem is tracked by DRILL-6545 and this Jira aims to fix the
problem with TopN
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