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[jOOQ/jOOQ#1049] Better GREATEST() and LEAST() emulations for SQL Server using MAX() or MIN() with VALUES() correlated derived table

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This commit is contained in:
Lukas Eder 2022-06-10 09:00:14 +02:00
parent 5b26e7b827
commit 74208f3398
3 changed files with 116 additions and 42 deletions
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31
jOOQ/src/main/java/org/jooq/impl/Greatest.java
View File

@ -54,15 +54,15 @@ import org.jooq.impl.QOM.UnmodifiableList;
*/
final class Greatest<T> extends AbstractField<T> implements QOM.Greatest<T> {
private final QueryPartListView<? extends Field<?>> args;
private final QueryPartListView<Field<T>> args;
@SuppressWarnings({ "unchecked", "rawtypes" })
Greatest(Field<?>... args) {
super(N_GREATEST, (DataType<T>) Tools.nullSafeDataType(args[0]));
this.args = QueryPartListView.wrap(args);
this.args = (QueryPartListView) QueryPartListView.wrap(args);
}
@SuppressWarnings("unchecked")
@Override
public final void accept(Context<?> ctx) {
@ -73,9 +73,11 @@ final class Greatest<T> extends AbstractField<T> implements QOM.Greatest<T> {
}
switch (ctx.family()) {
// This implementation has O(2^n) complexity. Better implementations
// are very welcome
// [#1049] TODO Fix this!
@ -84,22 +86,7 @@ final class Greatest<T> extends AbstractField<T> implements QOM.Greatest<T> {
case DERBY: {
Field<T> first = (Field<T>) args.get(0);
Field<T> other = (Field<T>) args.get(1);
if (args.size() > 2) {
Field<?>[] remaining = args.subList(2, args.size()).toArray(Tools.EMPTY_FIELD);
ctx.visit(DSL
.when(first.gt(other), DSL.greatest(first, remaining))
.otherwise(DSL.greatest(other, remaining)));
}
else
ctx.visit(DSL
.when(first.gt(other), first)
.otherwise(other));
return;
GreatestLeast.acceptCaseEmulation(ctx, args, DSL::greatest, Field::gt);
}
case FIREBIRD:

98
jOOQ/src/main/java/org/jooq/impl/GreatestLeast.java Normal file
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@ -0,0 +1,98 @@
/*
* Licensed 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.
*
* Other licenses:
* -----------------------------------------------------------------------------
* Commercial licenses for this work are available. These replace the above
* ASL 2.0 and offer limited warranties, support, maintenance, and commercial
* database integrations.
*
* For more information, please visit: http://www.jooq.org/licenses
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/
package org.jooq.impl;
import static org.jooq.impl.DSL.select;
import static org.jooq.impl.DSL.values;
import java.util.function.BiFunction;
import java.util.function.Function;
import org.jooq.Condition;
import org.jooq.Context;
import org.jooq.DataType;
import org.jooq.Field;
// ...
import org.jooq.Row1;
/**
* @author Lukas Eder
*/
final class GreatestLeast<T> {
static final <T> void acceptCaseEmulation(
Context<?> ctx,
QueryPartListView<Field<T>> args,
BiFunction<? super Field<T>, ? super Field<?>[], ? extends Field<T>> greatestLeast,
BiFunction<? super Field<T>, ? super Field<T>, ? extends Condition> gtLt
) {
// This implementation has O(2^n) complexity. Better implementations
// are very welcome
Field<T> first = args.get(0);
Field<T> other = args.get(1);
if (args.size() > 2) {
Field<?>[] remaining = args.subList(2, args.size()).toArray(Tools.EMPTY_FIELD);
ctx.visit(DSL
.when(gtLt.apply(first, other), greatestLeast.apply(first, remaining))
.otherwise(greatestLeast.apply(other, remaining)));
}
else
ctx.visit(DSL
.when(gtLt.apply(first, other), first)
.otherwise(other));
}
}

29
jOOQ/src/main/java/org/jooq/impl/Least.java
View File

@ -54,15 +54,15 @@ import org.jooq.impl.QOM.UnmodifiableList;
*/
final class Least<T> extends AbstractField<T> implements QOM.Least<T> {
private final QueryPartListView<? extends Field<?>> args;
private final QueryPartListView<Field<T>> args;
@SuppressWarnings({ "unchecked", "rawtypes" })
Least(Field<?>... args) {
super(N_LEAST, (DataType<T>) Tools.nullSafeDataType(args[0]));
this.args = QueryPartListView.wrap(args);
this.args = (QueryPartListView) QueryPartListView.wrap(args);
}
@SuppressWarnings("unchecked")
@Override
public final void accept(Context<?> ctx) {
@ -73,8 +73,11 @@ final class Least<T> extends AbstractField<T> implements QOM.Least<T> {
}
switch (ctx.family()) {
// This implementation has O(2^n) complexity. Better implementations
// are very welcome
@ -83,21 +86,7 @@ final class Least<T> extends AbstractField<T> implements QOM.Least<T> {
case DERBY: {
Field<T> first = (Field<T>) args.get(0);
Field<T> other = (Field<T>) args.get(1);
if (args.size() > 2) {
Field<?>[] remaining = args.subList(2, args.size()).toArray(Tools.EMPTY_FIELD);
ctx.visit(DSL
.when(first.lt(other), DSL.least(first, remaining))
.otherwise(DSL.least(other, remaining)));
}
else
ctx.visit(DSL
.when(first.lt(other), first)
.otherwise(other));
GreatestLeast.acceptCaseEmulation(ctx, args, DSL::least, Field::lt);
return;
}