GH-8760 Postgres: using DELETE ... RETURNING

Fixes https://github.com/spring-projects/spring-integration/issues/8760

* Make `PostgresChannelMessageStoreQueryProvider` to use single `DELETE ... RETURNING` for polling statements
* Add `isUsingSingleStatementForPoll` and use it from `JdbcChannelMessageStore`
* Execute Postgres init scripts to `PostgresContainerTest`
* Code clean up
* Document the new feature

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/channel/PostgresChannelMessageTableSubscriberTests.java

@@ -67,21 +67,6 @@ import static org.assertj.core.api.Assertions.assertThat;
 public class PostgresChannelMessageTableSubscriberTests implements PostgresContainerTest {
 
 	private static final String INTEGRATION_DB_SCRIPTS = """
-			CREATE SEQUENCE INT_MESSAGE_SEQ START WITH 1 INCREMENT BY 1 NO CYCLE;
-			^^^ END OF SCRIPT ^^^
-
-			CREATE TABLE INT_CHANNEL_MESSAGE (
-				MESSAGE_ID CHAR(36) NOT NULL,
-				GROUP_KEY CHAR(36) NOT NULL,
-				CREATED_DATE BIGINT NOT NULL,
-				MESSAGE_PRIORITY BIGINT,
-				MESSAGE_SEQUENCE BIGINT NOT NULL DEFAULT nextval('INT_MESSAGE_SEQ'),
-				MESSAGE_BYTES BYTEA,
-				REGION VARCHAR(100) NOT NULL,
-				constraint INT_CHANNEL_MESSAGE_PK primary key (REGION, GROUP_KEY, CREATED_DATE, MESSAGE_SEQUENCE)
-			);
-			^^^ END OF SCRIPT ^^^
-
 			CREATE FUNCTION INT_CHANNEL_MESSAGE_NOTIFY_FCT()
 			RETURNS TRIGGER AS
 			$BODY$

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/channel/PostgresContainerTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,14 +27,17 @@ import org.testcontainers.junit.jupiter.Testcontainers;
  * Since the Postgres container instance is shared via static property, it is going to be
  * started only once per JVM, therefore the target Docker container is reused automatically.
  *
+ * @author Artem Bilan
  * @author Rafael Winterhalter
+ * @author Johannes Edmeier
  *
  * @since 6.0
  */
 @Testcontainers(disabledWithoutDocker = true)
 public interface PostgresContainerTest {
 
-	PostgreSQLContainer<?> POSTGRES_CONTAINER = new PostgreSQLContainer<>("postgres:11");
+	PostgreSQLContainer<?> POSTGRES_CONTAINER = new PostgreSQLContainer<>("postgres:11")
+			.withInitScript("org/springframework/integration/jdbc/schema-postgresql.sql");
 
 	@BeforeAll
 	static void startContainer() {

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/store/channel/PostgresJdbcChannelMessageStoreTests.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.
+ */
+
+package org.springframework.integration.jdbc.store.channel;
+
+import javax.sql.DataSource;
+
+import org.apache.commons.dbcp2.BasicDataSource;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.integration.jdbc.channel.PostgresContainerTest;
+import org.springframework.jdbc.datasource.DataSourceTransactionManager;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.transaction.PlatformTransactionManager;
+
+/**
+ * @author Johannes Edmeier
+ * @author Artem Bilan
+ *
+ * @since 6.2
+ */
+@ContextConfiguration
+public class PostgresJdbcChannelMessageStoreTests extends AbstractJdbcChannelMessageStoreTests
+		implements PostgresContainerTest {
+
+	@Configuration
+	public static class Config {
+
+		@Bean
+		public DataSource dataSource() {
+			BasicDataSource dataSource = new BasicDataSource();
+			dataSource.setUrl(PostgresContainerTest.getJdbcUrl());
+			dataSource.setUsername(PostgresContainerTest.getUsername());
+			dataSource.setPassword(PostgresContainerTest.getPassword());
+			return dataSource;
+		}
+
+		@Bean
+		PlatformTransactionManager transactionManager(DataSource dataSource) {
+			return new DataSourceTransactionManager(dataSource);
+		}
+
+		@Bean
+		PostgresChannelMessageStoreQueryProvider queryProvider() {
+			return new PostgresChannelMessageStoreQueryProvider();
+		}
+
+	}
+
+}