Workaround MySQL limitation for batched correlated fetch

Author: beikov

core/impl/src/main/java/com/blazebit/persistence/impl/CriteriaBuilderConfigurationImpl.java

@@ -18,6 +18,7 @@
 import com.blazebit.persistence.impl.dialect.OracleDbmsDialect;
 import com.blazebit.persistence.impl.dialect.PostgreSQLDbmsDialect;
 import com.blazebit.persistence.impl.function.alias.AliasFunction;
+import com.blazebit.persistence.impl.function.inwrapper.InWrapperFunction;
 import com.blazebit.persistence.impl.function.base64.Base64Function;
 import com.blazebit.persistence.impl.function.base64.PostgreSQLBase64Function;
 import com.blazebit.persistence.impl.function.cast.CastFunction;
@@ -1657,6 +1658,11 @@ private void loadInternalFunctions() {
         jpqlFunctionGroup.add(null, new AliasFunction());
         registerFunction(jpqlFunctionGroup);
 
+        // in_wrapper function
+        jpqlFunctionGroup = new JpqlFunctionGroup(InWrapperFunction.FUNCTION_NAME, false);
+        jpqlFunctionGroup.add(null, new InWrapperFunction());
+        registerFunction(jpqlFunctionGroup);
+
         // column trunc function
         jpqlFunctionGroup = new JpqlFunctionGroup(ColumnTruncFunction.FUNCTION_NAME, false);
         jpqlFunctionGroup.add(null, new ColumnTruncFunction());

core/impl/src/main/java/com/blazebit/persistence/impl/function/inwrapper/InWrapperFunction.java

@@ -0,0 +1,47 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Blazebit
+ */
+
+package com.blazebit.persistence.impl.function.inwrapper;
+
+import com.blazebit.persistence.spi.FunctionRenderContext;
+import com.blazebit.persistence.spi.JpqlFunction;
+
+/**
+ *
+ * @author Christian Beikov
+ * @since 2.0.0
+ */
+public class InWrapperFunction implements JpqlFunction {
+
+    public static final String FUNCTION_NAME = "in_wrapper";
+
+    @Override
+    public boolean hasArguments() {
+        return true;
+    }
+
+    @Override
+    public boolean hasParenthesesIfNoArguments() {
+        return true;
+    }
+
+    @Override
+    public Class<?> getReturnType(Class<?> firstArgumentType) {
+        return firstArgumentType;
+    }
+
+    @Override
+    public void render(FunctionRenderContext context) {
+        int size = context.getArgumentsSize();
+        if (size != 2) {
+            throw new RuntimeException("The " + FUNCTION_NAME + " function needs exactly two argument!");
+        }
+        context.addChunk("1 and ");
+        context.addArgument(0);
+        context.addChunk(" in (select * from ");
+        context.addArgument(1);
+        context.addChunk(" tmp_)");
+    }
+}

entity-view/impl/src/main/java/com/blazebit/persistence/view/impl/objectbuilder/transformer/correlation/SubqueryCorrelationBuilder.java

@@ -141,7 +141,11 @@ public JoinOnBuilder<CorrelationQueryBuilder> correlate(Class<?> entityClass) {
                     if (limiter.getLimitValue() != null && limiter.getLimitValue() == 1) {
                         subqueryBuilder = criteriaBuilder.where(correlationExternalAlias).eq().from(entityClass, correlationAlias);
                     } else {
-                        subqueryBuilder = criteriaBuilder.where(correlationExternalAlias).in().from(entityClass, correlationAlias);
+                        if (getService(DbmsDialect.class).supportsLimitInQuantifiedPredicateSubquery()) {
+                            subqueryBuilder = criteriaBuilder.where(correlationExternalAlias).in().from(entityClass, correlationAlias);
+                        } else {
+                            subqueryBuilder = criteriaBuilder.where("1").eq("subqueryAlias_","FUNCTION('in_wrapper', " + correlationExternalAlias + ", subqueryAlias_)").from(entityClass, correlationAlias);
+                        }
                     }
                     limiter.apply(parameterHolder, optionalParameters, subqueryBuilder);
                     this.correlationBuilder = subqueryBuilder;