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https://issues.apache.org/jira/browse/CALCITE-7062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17995810#comment-17995810
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Julian Hyde commented on CALCITE-7062:
--------------------------------------
A fix would be much appreciated.
Regarding the test case that accompanies the fix. The test case should not use
DDL unless DDL is essential to reproduce the issue (i.e. part of the one-line
summary of the bug). I hope that the test case is not in {{ServerTest.java}}
but is instead in one of the {{.iq}} files under {{core}}.
> Row type of UNION may ignore a column's nullability
> ---------------------------------------------------
>
> Key: CALCITE-7062
> URL: https://issues.apache.org/jira/browse/CALCITE-7062
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.39.0, 1.40.0
> Reporter: Vladimir Steshin
> Priority: Minor
>
> Reproducer:
> {code:java}
> package org.apache.calcite.test;
> class ServerTest {
> @Test void testNullableCoercionInUnion() throws Exception {
> try (Connection c = connect(); Statement s = c.createStatement()) {
> s.execute("create table t(a DATE)");
> try (ResultSet r = s.executeQuery("SELECT a FROM t UNION ALL select
> CURRENT_TIMESTAMP")) {
> assertTrue(r.next());
> assertFalse(r.next());
> }
> }
> }
> // Or
> @Test void test2() throws Exception {
> try (Connection c = connect(); Statement s = c.createStatement()) {
> s.execute("create table t1(id int not null, test TIMESTAMP NOT NULL)");
> s.execute("create table t2(id int not null, test VARCHAR)");
> s.execute("insert into t1 values (1, SYSTIMESTAMP)");
> s.execute("insert into t2 values (1, CAST(SYSDATE AS VARCHAR))");
> String query = "SELECT cast(test as date) as test FROM t2 " +
> "UNION ALL " +
> "select test from t1";
> s.execute(query);
> }
> }{code}
> Failure:
> {code:java}
> Conversion to relational algebra failed to preserve datatypes:
> validated type:
> RecordType(TIMESTAMP(0) NOT NULL A) NOT NULL
> converted type:
> RecordType(TIMESTAMP(0) A) NOT NULL
> rel:
> LogicalUnion(all=[true])
> LogicalProject(A=[CAST($0):TIMESTAMP(0)])
> LogicalTableScan(table=[[T]])
> LogicalProject(CURRENT_TIMESTAMP=[CURRENT_TIMESTAMP])
> LogicalValues(tuples=[[{ 0 }]])
> at
> org.apache.calcite.sql2rel.SqlToRelConverter.checkConvertedType(SqlToRelConverter.java:524)
> at
> org.apache.calcite.sql2rel.SqlToRelConverter.convertQuery(SqlToRelConverter.java:643)
> at org.apache.calcite.prepare.Prepare.prepareSql(Prepare.java:258) at
> org.apache.calcite.prepare.Prepare.prepareSql(Prepare.java:221) at
> org.apache.calcite.prepare.CalcitePrepareImpl.prepare2_(CalcitePrepareImpl.java:673)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl.prepare_(CalcitePrepareImpl.java:524)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl.prepareSql(CalcitePrepareImpl.java:492)
> at
> org.apache.calcite.jdbc.CalciteConnectionImpl.parseQuery(CalciteConnectionImpl.java:246)
> at
> org.apache.calcite.jdbc.CalciteMetaImpl.prepareAndExecute(CalciteMetaImpl.java:654){code}
> Regarding my research, the nullability is lost somewhere around
> {code:java}
> class AbstractTypeCoercion
> RelDataType syncAttributes(
> RelDataType fromType,
> RelDataType toType) {
> RelDataType syncedType = toType;
> if (fromType != null) {
> syncedType = factory.createTypeWithNullability(syncedType,
> fromType.isNullable());
> ...
> }{code}
> It doesn't take in account {_}toType.isNullable(){_}.
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