[#6817] Add DSL.noCondition()

jOOQ-examples/jOOQ-spark-chart-example/src/main/java/org/jooq/example/chart/SakilaReportService.java

@@ -194,7 +194,7 @@ private static Route rentalsPerCategory() {
      */
     private static Condition storeIdCondition(Request req) {
         return storeIdAll(req)
-            ? trueCondition()
+            ? noCondition()
             : STORE.STORE_ID.eq(val(req.queryParams("storeId"), int.class));
     }
 
@@ -210,7 +210,7 @@ private static boolean storeIdAll(Request req) {
      */
     private static Condition countryIdCondition(Request req) {
         return countryIdAll(req)
-            ? trueCondition()
+            ? noCondition()
             : COUNTRY.COUNTRY_ID.eq(val(req.queryParams("countryId"), int.class));
     }
 
@@ -219,7 +219,7 @@ private static Condition countryIdCondition(Request req) {
      */
     private static Condition countryIdSemiJoinCondition(Request req) {
         return countryIdAll(req)
-            ? trueCondition()
+            ? noCondition()
             : RENTAL.CUSTOMER_ID.in(
                 select(CUSTOMER.CUSTOMER_ID)
                 .from(CUSTOMER)

jOOQ-meta/src/main/java/org/jooq/util/firebird/FirebirdDatabase.java

@@ -38,8 +38,8 @@
 import static org.jooq.impl.DSL.decode;
 import static org.jooq.impl.DSL.falseCondition;
 import static org.jooq.impl.DSL.inline;
+import static org.jooq.impl.DSL.noCondition;
 import static org.jooq.impl.DSL.select;
-import static org.jooq.impl.DSL.trueCondition;
 import static org.jooq.util.firebird.rdb.Tables.RDB$GENERATORS;
 import static org.jooq.util.firebird.rdb.Tables.RDB$INDEX_SEGMENTS;
 import static org.jooq.util.firebird.rdb.Tables.RDB$PROCEDURES;
@@ -246,7 +246,7 @@ protected List<TableDefinition> getTables0() throws SQLException {
                     // "selectable" procedures
                     .where(RDB$PROCEDURES.RDB$PROCEDURE_TYPE.eq((short) 1))
                     .and(tableValuedFunctions()
-                        ? trueCondition()
+                        ? noCondition()
                         : falseCondition())
                 )
                 .orderBy(1)) {

jOOQ-meta/src/main/java/org/jooq/util/postgres/PostgresDatabase.java

@@ -44,13 +44,13 @@
 import static org.jooq.impl.DSL.inline;
 import static org.jooq.impl.DSL.max;
 import static org.jooq.impl.DSL.name;
+import static org.jooq.impl.DSL.noCondition;
 import static org.jooq.impl.DSL.not;
 import static org.jooq.impl.DSL.one;
 import static org.jooq.impl.DSL.partitionBy;
 import static org.jooq.impl.DSL.row;
 import static org.jooq.impl.DSL.rowNumber;
 import static org.jooq.impl.DSL.select;
-import static org.jooq.impl.DSL.trueCondition;
 import static org.jooq.impl.DSL.when;
 import static org.jooq.util.postgres.PostgresDSL.array;
 import static org.jooq.util.postgres.PostgresDSL.arrayAppend;
@@ -764,7 +764,7 @@ protected List<RoutineDefinition> getRoutines0() throws SQLException {
             .where(r1.ROUTINE_SCHEMA.in(getInputSchemata()))
             .and(tableValuedFunctions()
                     ? condition(not(PG_PROC.PRORETSET))
-                    : trueCondition())
+                    : noCondition())
             .orderBy(
                 r1.ROUTINE_SCHEMA.asc(),
                 r1.ROUTINE_NAME.asc(),

jOOQ/src/main/java/org/jooq/impl/CombinedCondition.java

@@ -40,6 +40,7 @@
 import static org.jooq.Clause.CONDITION_OR;
 import static org.jooq.Operator.AND;
 import static org.jooq.impl.DSL.falseCondition;
+import static org.jooq.impl.DSL.noCondition;
 import static org.jooq.impl.DSL.trueCondition;
 import static org.jooq.impl.Keywords.K_AND;
 import static org.jooq.impl.Keywords.K_OR;
@@ -66,6 +67,41 @@ final class CombinedCondition extends AbstractCondition {
     private final Operator        operator;
     private final List<Condition> conditions;
 
+    static Condition of(Operator operator, Condition left, Condition right) {
+        if (left instanceof NoCondition)
+            return right;
+        else if (right instanceof NoCondition)
+            return left;
+        else
+            return new CombinedCondition(operator, left, right);
+    }
+
+    static Condition of(Operator operator, Collection<? extends Condition> conditions) {
+        if (conditions.isEmpty())
+            return noCondition();
+
+        CombinedCondition result = null;
+        Condition first = null;
+
+        for (Condition condition : conditions)
+            if (!(condition instanceof NoCondition))
+                if (first == null)
+                    first = condition;
+                else if (result == null)
+                    (result = new CombinedCondition(operator, conditions.size()))
+                        .add(operator, first)
+                        .add(operator, condition);
+                else
+                    result.add(operator, condition);
+
+        if (result != null)
+            return result;
+        else if (first != null)
+            return first;
+        else
+            return noCondition();
+    }
+
     private CombinedCondition(Operator operator, int size) {
         if (operator == null)
             throw new IllegalArgumentException("The argument 'operator' must not be null");
@@ -74,21 +110,14 @@ private CombinedCondition(Operator operator, int size) {
         this.conditions = new ArrayList<Condition>(size);
     }
 
-    CombinedCondition(Operator operator, Condition left, Condition right) {
+    private CombinedCondition(Operator operator, Condition left, Condition right) {
         this(operator, 2);
 
         add(operator, left);
         add(operator, right);
     }
 
-    CombinedCondition(Operator operator, Collection<? extends Condition> conditions) {
-        this(operator, conditions.size());
-
-        for (Condition condition : conditions)
-            add(operator, condition);
-    }
-
-    private final void add(Operator op, Condition condition) {
+    private final CombinedCondition add(Operator op, Condition condition) {
         if (condition instanceof CombinedCondition) {
             CombinedCondition combinedCondition = (CombinedCondition) condition;
 
@@ -101,6 +130,8 @@ else if (condition == null)
             throw new IllegalArgumentException("The argument 'conditions' must not contain null");
         else
             this.conditions.add(condition);
+
+        return this;
     }
 
     @Override

jOOQ/src/main/java/org/jooq/impl/ConditionProviderImpl.java

@@ -35,7 +35,7 @@
 
 package org.jooq.impl;
 
-import static org.jooq.impl.DSL.trueCondition;
+import static org.jooq.impl.DSL.noCondition;
 
 import java.util.Arrays;
 import java.util.Collection;
@@ -64,11 +64,11 @@ final class ConditionProviderImpl extends AbstractQueryPart implements Condition
     }
 
     final Condition getWhere() {
-        return hasWhere() ? condition : trueCondition();
+        return hasWhere() ? condition : noCondition();
     }
 
     final boolean hasWhere() {
-        return condition != null;
+        return condition != null && !(condition instanceof NoCondition);
     }
 
     // -------------------------------------------------------------------------

jOOQ/src/main/java/org/jooq/impl/DSL.java

@@ -10333,6 +10333,37 @@ public static Condition condition(Record record) {
     // XXX Global Condition factory
     // -------------------------------------------------------------------------
 
+    /**
+     * Return a <code>Condition</code> that behaves like no condition being
+     * present.
+     * <p>
+     * This is useful as an "identity" condition for reduction operations, for
+     * both <code>AND</code> and <code>OR</code> reductions, e.g.
+     * <p>
+     * <code><pre>
+     * Condition combined =
+     * Stream.of(cond1, cond2, cond3)
+     *       .reduce(noCondition(), Condition::and);
+     * </pre></code>
+     * <p>
+     * When this condition is passed to SQL clauses, such as the
+     * <code>WHERE</code> clause, the entire clause is omitted:
+     * <p>
+     * <code><pre>
+     * selectFrom(T).where(noCondition())
+     * </pre></code>
+     * <p>
+     * ... will produce
+     * <p>
+     * <code><pre>
+     * SELECT * FROM t
+     * </pre></code>
+     */
+    @Support
+    public static Condition noCondition() {
+        return NoCondition.INSTANCE;
+    }
+
     /**
      * Return a <code>Condition</code> that will always evaluate to true.
      */
@@ -10409,7 +10440,7 @@ public static Condition or(Collection<? extends Condition> conditions) {
      */
     @Support
     public static Condition condition(Operator operator, Condition left, Condition right) {
-        return new CombinedCondition(operator, left, right);
+        return CombinedCondition.of(operator, left, right);
     }
 
     /**
@@ -10427,7 +10458,7 @@ public static Condition condition(Operator operator, Condition... conditions) {
      */
     @Support
     public static Condition condition(Operator operator, Collection<? extends Condition> conditions) {
-        return new CombinedCondition(operator, conditions);
+        return CombinedCondition.of(operator, conditions);
     }
 
     /**

jOOQ/src/main/java/org/jooq/impl/DefaultDSLContext.java

@@ -47,7 +47,6 @@
 import static org.jooq.impl.DSL.sequence;
 import static org.jooq.impl.DSL.sql;
 import static org.jooq.impl.DSL.table;
-import static org.jooq.impl.DSL.trueCondition;
 import static org.jooq.impl.DSL.zero;
 import static org.jooq.impl.Tools.EMPTY_QUERY;
 import static org.jooq.impl.Tools.EMPTY_TABLE_RECORD;
@@ -3993,7 +3992,7 @@ public int fetchCount(Select<?> query) {
 
     @Override
     public int fetchCount(Table<?> table) {
-        return fetchCount(table, trueCondition());
+        return selectCount().from(table).fetchOne(0, int.class);
     }
 
     @Override
@@ -4008,7 +4007,7 @@ public boolean fetchExists(Select<?> query) throws DataAccessException {
 
     @Override
     public boolean fetchExists(Table<?> table) throws DataAccessException {
-        return fetchExists(table, trueCondition());
+        return fetchExists(selectOne().from(table));
     }
 
     @Override
@@ -4035,7 +4034,7 @@ public int execute(Query query) {
 
     @Override
     public <R extends Record> Result<R> fetch(Table<R> table) {
-        return fetch(table, trueCondition());
+        return selectFrom(table).fetch();
     }
 
     @Override
@@ -4087,7 +4086,7 @@ public <R extends Record> R fetchAny(Table<R> table, Condition condition) {
 
     @Override
     public <R extends Record> Cursor<R> fetchLazy(Table<R> table) {
-        return fetchLazy(table, trueCondition());
+        return selectFrom(table).fetchLazy();
     }
 
     @Override
@@ -4119,7 +4118,7 @@ public <R extends Record> CompletionStage<Result<R>> fetchAsync(Executor executo
 
     @Override
     public <R extends Record> Stream<R> fetchStream(Table<R> table) {
-        return fetchStream(table, trueCondition());
+        return selectFrom(table).stream();
     }
 
     @Override

jOOQ/src/main/java/org/jooq/impl/NoCondition.java

@@ -0,0 +1,64 @@
+/*
+ * 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.Clause.CONDITION;
+import static org.jooq.Clause.CONDITION_COMPARISON;
+
+import org.jooq.Clause;
+import org.jooq.Context;
+
+/**
+ * @author Lukas Eder
+ */
+final class NoCondition extends AbstractCondition {
+
+    private static final long     serialVersionUID = 775364624704563687L;
+    private static final Clause[] CLAUSES          = { CONDITION, CONDITION_COMPARISON };
+    static final NoCondition      INSTANCE         = new NoCondition();
+
+    @Override
+    public final void accept(Context<?> ctx) {
+        ctx.sql("1 = 1");
+    }
+
+    @Override
+    public final Clause[] clauses(Context<?> ctx) {
+        return CLAUSES;
+    }
+
+    private NoCondition() {}
+}

jOOQ/src/main/java/org/jooq/impl/Pivot.java

@@ -35,7 +35,7 @@
 package org.jooq.impl;
 
 import static org.jooq.conf.ParamType.INLINED;
-import static org.jooq.impl.DSL.trueCondition;
+import static org.jooq.impl.DSL.noCondition;
 import static org.jooq.impl.DSL.using;
 import static org.jooq.impl.Keywords.K_FOR;
 import static org.jooq.impl.Keywords.K_IN;
@@ -177,11 +177,10 @@ private Table<Record> select(Configuration configuration) {
             List<Field<?>> aggregationSelects = new ArrayList<Field<?>>();
             for (Field<?> inField : in) {
                 for (Field<?> aggregateFunction : aggregateFunctions) {
-                    Condition join = trueCondition();
+                    Condition join = noCondition();
 
-                    for (Field<?> field : groupingFields) {
+                    for (Field<?> field : groupingFields)
                         join = join.and(condition(pivot, field));
-                    }
 
                     @SuppressWarnings("unchecked")
                     Select<?> aggregateSelect = using(configuration)