Vladimir Ozerov created IGNITE-8579:
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Summary: SQL: Unicast request with LIMIT should skip merge table
if possible
Key: IGNITE-8579
URL: https://issues.apache.org/jira/browse/IGNITE-8579
Project: Ignite
Issue Type: Task
Components: sql
Affects Versions: 2.5
Reporter: Vladimir Ozerov
Fix For: 2.6
*Problem*
We have two cases when request could be executed only over a single partition:
1) With explicit partition
2) When partition pruning optimization reduced request to a single partition
(IGNITE-4509). E.g. if {{department_id}} is affinity key in the query below:
{code}
SELECT * FROM emp WHERE department_id=? LIMIT 50;
{code}
In both cases we need to ensure that instead of fully-fledged two-step
execution, we perform only map request, and reduce phase is skipped. I.e.
{{org.apache.ignite.internal.processors.cache.query.GridCacheTwoStepQuery#skipMergeTbl}}
is resolved to true.
*Reproducer*
The following query reproduces a situation when this is not the case at the
moment, and merge table is initialized
{code}
CREATE TABLE emp (pk_id BIGINT, dept_ID BIGINT, name VARCHAR, PRIMARY
KEY(pk_id, dept_id) WITH "AFFINITY_KEY=dept_id";
SELECT * FROM emp WHERE dept_id=? LIMIT 10
{code}
Notice that reduce phase exists, while in reality it is not needed.
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