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[CALCITE-6678] Calcite should support dual table query when db provides this feature #4056

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[CALCITE-6678] Calcite should support dual table query when db provides this feature #4056

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[CALCITE-6678] Calcite should support dual table query when db provid…
strongduanmu Nov 20, 2024
eef87e0
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strongduanmu Nov 20, 2024
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34 changes: 6 additions & 28 deletions core/src/main/java/org/apache/calcite/jdbc/CalciteConnectionImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@

import org.apache.calcite.DataContext;
import org.apache.calcite.DataContexts;
import org.apache.calcite.adapter.java.AbstractQueryableTable;
import org.apache.calcite.adapter.java.JavaTypeFactory;
import org.apache.calcite.avatica.AvaticaConnection;
import org.apache.calcite.avatica.AvaticaFactory;
Expand All @@ -37,7 +36,6 @@
import org.apache.calcite.linq4j.BaseQueryable;
import org.apache.calcite.linq4j.Enumerable;
import org.apache.calcite.linq4j.Enumerator;
import org.apache.calcite.linq4j.Linq4j;
import org.apache.calcite.linq4j.Ord;
import org.apache.calcite.linq4j.QueryProvider;
import org.apache.calcite.linq4j.Queryable;
Expand All @@ -48,8 +46,6 @@
import org.apache.calcite.plan.RelOptUtil;
import org.apache.calcite.prepare.CalciteCatalogReader;
import org.apache.calcite.rel.type.DelegatingTypeSystem;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeFactory;
import org.apache.calcite.rel.type.RelDataTypeSystem;
import org.apache.calcite.rel.type.TimeFrameSet;
import org.apache.calcite.rel.type.TimeFrames;
Expand All @@ -59,6 +55,7 @@
import org.apache.calcite.schema.Schemas;
import org.apache.calcite.schema.impl.AbstractSchema;
import org.apache.calcite.schema.impl.LongSchemaVersion;
import org.apache.calcite.schema.impl.ViewTable;
import org.apache.calcite.server.CalciteServer;
import org.apache.calcite.server.CalciteServerStatement;
import org.apache.calcite.sql.advise.SqlAdvisor;
Expand All @@ -80,7 +77,6 @@
import java.lang.reflect.Type;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
Expand Down Expand Up @@ -156,7 +152,11 @@ protected CalciteConnectionImpl(Driver driver, AvaticaFactory factory,
: CalciteSchema.createRootSchema(true));
// Add dual table metadata when isSupportedDualTable return true
if (cfg.conformance().isSupportedDualTable()) {
this.rootSchema.add("DUAL", new DualTable(String.class));
SchemaPlus schemaPlus = this.rootSchema.plus();
// Dual table contains one row with a value X
schemaPlus.add(
"DUAL", ViewTable.viewMacro(schemaPlus, "VALUES ('X')",
ImmutableList.of(), null, false));
}
checkArgument(this.rootSchema.isRoot(), "must be root schema");
this.properties.put(InternalProperty.CASE_SENSITIVE, cfg.caseSensitive());
Expand Down Expand Up @@ -629,26 +629,4 @@ static class CalciteServerStatementImpl
this.iterator = iterator;
}
}

/** Implementation of {@link AbstractQueryableTable} for dual table. */
private static class DualTable extends AbstractQueryableTable {

DualTable(Class<String> clazz) {
super(clazz);
}

@Override public RelDataType getRowType(RelDataTypeFactory typeFactory) {
return typeFactory.createStructType(
// Dual table has one column DUMMY, and defined to be VARCHAR2(1)
Collections.singletonList(typeFactory.createJavaType(String.class)),
Collections.singletonList("DUMMY"));
}

@SuppressWarnings("unchecked")
@Override public Queryable<String> asQueryable(QueryProvider queryProvider,
SchemaPlus schema, String tableName) {
// Dual table contains one row with a value X
return Linq4j.asEnumerable(Collections.singletonList("X")).asQueryable();
}
}
}
72 changes: 72 additions & 0 deletions core/src/test/resources/sql/dual-table-query.iq
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@@ -0,0 +1,72 @@
# dual-table-query.iq - Tests for DUAL table query
#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to you under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

# [CALCITE-6678] Support dual table query (enabled in MySQL, Oracle libraries)
!set outputformat mysql
!use scott-mysql

# MySQL supports users to specify the dual table, and also supports users not to specify the dual table.
SELECT 1 + 1 FROM DUAL;
+--------+
| EXPR$0 |
+--------+
| 2 |
+--------+
(1 row)

!ok

SELECT 1 + 1;
+--------+
| EXPR$0 |
+--------+
| 2 |
+--------+
(1 row)

!ok

# Oracle supports users to specify the dual table, but not supports users not to specify the dual table.
!use scott-oracle

SELECT 1 + 1 FROM DUAL;
+--------+
| EXPR$0 |
+--------+
| 2 |
+--------+
(1 row)

!ok

SELECT 1 + 1;
java.sql.SQLException: Error while executing SQL "SELECT 1 + 1": From line 1, column 1 to line 1, column 12: SELECT must have a FROM clause

!error

SELECT * FROM DUAL;
+--------+
| EXPR$0 |
+--------+
| X |
+--------+
(1 row)

!ok

# End dual-table-query.iq
55 changes: 1 addition & 54 deletions core/src/test/resources/sql/dummy.iq
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Expand Up @@ -20,58 +20,5 @@ values 1;
EXPR$0
1
!ok

strongduanmu marked this conversation as resolved.
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# [CALCITE-6678] Support dual table query (enabled in MySQL, Oracle libraries)
!set outputformat mysql
!use scott-mysql

# MySQL supports users to specify the dual table, and also supports users not to specify the dual table.
SELECT 1 + 1 FROM DUAL;
+--------+
| EXPR$0 |
+--------+
| 2 |
+--------+
(1 row)

!ok

SELECT 1 + 1;
+--------+
| EXPR$0 |
+--------+
| 2 |
+--------+
(1 row)

!ok

# Oracle supports users to specify the dual table, but not supports users not to specify the dual table.
!use scott-oracle

SELECT 1 + 1 FROM DUAL;
+--------+
| EXPR$0 |
+--------+
| 2 |
+--------+
(1 row)

!ok

SELECT 1 + 1;
java.sql.SQLException: Error while executing SQL "SELECT 1 + 1": From line 1, column 1 to line 1, column 12: SELECT must have a FROM clause

!error

SELECT * FROM DUAL;
+-------+
| DUMMY |
+-------+
| X |
+-------+
(1 row)

!ok

# do not modify this file, this is intended only for temporary debugging code
# End dummy.iq
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