Vladimir Ozerov created IGNITE-8732:
---------------------------------------
Summary: SQL: REPLICATED cache cannot be left-joined to PARTITIONED
Key: IGNITE-8732
URL: https://issues.apache.org/jira/browse/IGNITE-8732
Project: Ignite
Issue Type: Bug
Components: sql
Affects Versions: 2.5
Reporter: Vladimir Ozerov
*Steps to reproduce*
# Run
{{org.apache.ignite.sqltests.ReplicatedSqlTest#testLeftJoinReplicatedPartitioned}}
# Observe that we have 2x results on 2-node cluster
*Root Cause*
{{left LEFT JOIN right ON cond}} operation assumes full scan of of a left
expression. Currently we perform this scan on every node and then simply merge
results on reducer. Two nodes, two scans of {{REPLICATED}} cache, 2x results.
*Solution*
We may consider several solutions. Deeper analysis is required to understand
which is the right one.
# Perform deduplication on reducer
# Treat {{REPLICATED}} cache as {{PARTITIONED}}. Essentially, we just need to
pass proper backup filter. But what if {{REPLICATED}} cache spans more nodes
than {{PARTITIONED}}? We cannot rely on primary/backup in this case
# Implement additional execution phase as follows:
{code}
SELECT left.cols, right.cols FROM left INNER JOIN right ON cond; // Get common
part
UNION
SELECT left.cols, [NULL].cols FROM left WHERE left.id NOT IN ([ids from the
first phase])
{code}
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
