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Posted to issues@ignite.apache.org by "Vladimir Ozerov (JIRA)" <ji...@apache.org> on 2018/06/07 09:45:00 UTC
[jira] [Updated] (IGNITE-8732) SQL: REPLICATED cache cannot be
left-joined to PARTITIONED
[ https://issues.apache.org/jira/browse/IGNITE-8732?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Vladimir Ozerov updated IGNITE-8732:
------------------------------------
Description:
*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 "inner join" part
UNION
SELECT left.cols, [NULL].cols FROM left WHERE left.id NOT IN ([ids from the first phase]) // Get "outer join" part
{code}
was:
*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}
> 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
> Priority: Major
>
> *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 "inner join" part
> UNION
> SELECT left.cols, [NULL].cols FROM left WHERE left.id NOT IN ([ids from the first phase]) // Get "outer join" part
> {code}
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