Maksim Zhuravkov created IGNITE-21372:
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Summary: Sql. Do not execute queries that guaranteed to return
none results.
Key: IGNITE-21372
URL: https://issues.apache.org/jira/browse/IGNITE-21372
Project: Ignite
Issue Type: Improvement
Components: sql
Affects Versions: 3.0.0-beta2
Reporter: Maksim Zhuravkov
{code:java}
sql("CREATE TABLE t2 (id INTEGER PRIMARY KEY, val INTEGER)");
// Query that never returns a result:
sql("SELECT * FROM t2 WHERE id IS NULL");
// Plan
IgniteExchange(distribution=[single]): rowcount = 2500.0, cumulative cost =
IgniteCost [rowCount=12500.0, cpu=42500.0, memory=0.0, io=0.0,
network=20000.0], id = 28
IgniteTableScan(table=[[PUBLIC, T2]], tableId=[8], *filters=[false]*,
requiredColumns=[{0, 1}]): rowcount = 2500.0, cumulative cost = IgniteCost
[rowCount=10000.0, cpu=40000.0, memory=0.0, io=0.0, network=0.0], id = 25
{code}
Although the optimizer is able deduce that `id is NULL` is always false, since
id is not nullable, and converted a predicate FALSE, the execution engine still
runs such a query.
It is possible reduce plans that are guaranteed to produce no results to some
form of an empty plan, so that the execution engine won't run them and return
an empty cursor instead.
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