HHH-16867 - support index and join hints in the CockroachDB dialect

hibernate-core/src/main/java/org/hibernate/dialect/CockroachDialect.java

@@ -14,6 +14,7 @@
 import java.time.temporal.TemporalAccessor;
 import java.util.Calendar;
 import java.util.Date;
+import java.util.List;
 import java.util.Map;
 import java.util.TimeZone;
 import java.util.regex.Matcher;
@@ -1079,6 +1080,33 @@ public SQLExceptionConversionDelegate buildSQLExceptionConversionDelegate() {
 		};
 	}
 
+	/**
+	 * Applies the hints to the query string.
+	 *
+	 * The hints can be <a href="https://www.cockroachlabs.com/docs/v23.1/table-expressions#force-index-selection">index selection hints</a>
+	 * or <a href="https://www.cockroachlabs.com/docs/stable/sql-grammar#opt_join_hint">join hints</a>.
+	 * <p>
+	 * For index selection hints, use the format {@code <tablename>@{FORCE_INDEX=<index>[,<DIRECTION>]}}
+	 * where the optional DIRECTION is either ASC (ascending) or DESC (descending). Multiple index hints can be provided.
+	 * The effect is that in the final SQL statement the hint is added to the table name mentioned in the hint.
+	 *<p>
+	 * For join hints, use the format {@code "<MERGE|HASH|LOOKUP|INVERTED> JOIN"}. Only one join hint will be added. It is
+	 * applied to all join statements in the SQL statement.
+	 * <p>
+	 * Hints are only added to select statements.
+	 *
+	 * @param query The query to which to apply the hint.
+	 * @param hintList The hints to apply
+	 *
+	 * @return the query with hints added
+	 */
+	@Override
+	public String getQueryHintString(String query, List<String> hintList) {
+		return new CockroachDialectQueryHints(query, hintList).getQueryHintString();
+	}
+
+
+
 // CockroachDB doesn't support this by default. See sql.multiple_modifications_of_table.enabled
 //
 //	@Override

hibernate-core/src/main/java/org/hibernate/dialect/CockroachDialectQueryHints.java

@@ -0,0 +1,131 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+
+package org.hibernate.dialect;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+class CockroachDialectQueryHints {
+
+	final private Pattern TABLE_QUERY_PATTERN = Pattern.compile(
+			"(?i)^\\s*(select\\b.+?\\bfrom\\b)(.+?)(\\bwhere\\b.+?)$" );
+	final private Pattern JOIN_HINT_PATTERN = Pattern.compile( "(?i)(MERGE|HASH|LOOKUP|INVERTED)\\s+JOIN" );
+
+	//If matched, group 1 contains everything before the join keyword.
+	final private Pattern JOIN_PATTERN = Pattern.compile(
+			"(?i)\\b(cross|natural\\s+(.*)\\b|(full|left|right)(\\s+outer)?)?\\s+join" );
+
+	final private String query;
+	final private List<String> hints;
+
+	public CockroachDialectQueryHints(String query, List<String> hintList) {
+		this.query = query;
+		this.hints = hintList;
+	}
+
+	public String getQueryHintString() {
+		List<IndexHint> indexHints = new ArrayList<>();
+		JoinHint joinHint = null;
+		for ( var h : hints ) {
+			IndexHint indexHint = parseIndexHints( h );
+			if ( indexHint != null ) {
+				indexHints.add( indexHint );
+				continue;
+			}
+			joinHint = parseJoinHints( h );
+		}
+
+		String result = addIndexHints( query, indexHints );
+		return joinHint == null ? result : addJoinHint( query, joinHint );
+	}
+
+	private IndexHint parseIndexHints(String hint) {
+		var parts = hint.split( "@" );
+		if ( parts.length == 2 ) {
+			return new IndexHint( parts[0], hint );
+		}
+		return null;
+	}
+
+	private JoinHint parseJoinHints(String hint) {
+		var matcher = JOIN_HINT_PATTERN.matcher( hint );
+		if ( matcher.find() ) {
+			return new JoinHint( matcher.group( 1 ) );
+		}
+		return null;
+	}
+
+	String addIndexHints(String query, List<IndexHint> hints) {
+
+		Matcher statementMatcher = TABLE_QUERY_PATTERN.matcher( query );
+
+		if ( statementMatcher.matches() && statementMatcher.groupCount() > 2 ) {
+			String prefix = statementMatcher.group( 1 );
+			String fromList = statementMatcher.group( 2 );
+			String suffix = statementMatcher.group( 3 );
+			fromList = addIndexHintsToFromList( fromList, hints );
+			return prefix + fromList + suffix;
+		}
+		else {
+			return query;
+		}
+	}
+
+	String addJoinHint(String query, JoinHint hint) {
+		var m = JOIN_PATTERN.matcher( query );
+		StringBuilder buffer = new StringBuilder();
+		int start = 0;
+		while ( m.find() ) {
+			buffer.append( query.substring( start, m.start() ) );
+
+			if ( m.group( 1 ) == null ) {
+				buffer.append( " inner" );
+			}
+			else {
+				buffer.append( m.group( 1 ) );
+			}
+			buffer.append( " " )
+					.append( hint.joinType )
+					.append( " join" );
+			start = m.end();
+		}
+		buffer.append( query.substring( start ) );
+		return buffer.toString();
+	}
+
+	String addIndexHintsToFromList(String fromList, List<IndexHint> hints) {
+		String result = fromList;
+		for ( var hint : hints ) {
+			result = result.replaceAll( "(?i)\\b" + hint.table + "\\b", hint.text );
+		}
+		return result;
+	}
+
+
+	static class IndexHint {
+		final String table;
+		final String text;
+
+		IndexHint(String table, String text) {
+			this.table = table;
+			this.text = text;
+		}
+
+	}
+
+	static class JoinHint {
+		final String joinType;
+
+		JoinHint(String type) {
+			this.joinType = type.toLowerCase( Locale.ROOT );
+		}
+	}
+}

hibernate-core/src/test/java/org/hibernate/orm/test/dialect/functional/CockroachDBQueryHintsTest.java

@@ -0,0 +1,182 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+
+package org.hibernate.orm.test.dialect.functional;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.hibernate.dialect.CockroachDialect;
+
+import org.hibernate.testing.jdbc.SQLStatementInspector;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.JiraKey;
+import org.hibernate.testing.orm.junit.RequiresDialect;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Index;
+import jakarta.persistence.JoinColumn;
+import jakarta.persistence.ManyToOne;
+import jakarta.persistence.OneToMany;
+import jakarta.persistence.Table;
+import jakarta.persistence.TypedQuery;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+@RequiresDialect(CockroachDialect.class)
+@SessionFactory(useCollectingStatementInspector = true)
+@DomainModel(annotatedClasses = {
+		SimpleEntity.class, ChildEntity.class
+})
+@JiraKey("HHH-16867")
+public class CockroachDBQueryHintsTest {
+
+	@BeforeAll
+	public void setUp(SessionFactoryScope scope) {
+		scope.inTransaction( session -> {
+			var se1 = new SimpleEntity( 1, "se1" );
+			se1.addChild( new ChildEntity( "se1child1" ) );
+			session.persist( se1 );
+			var se2 = new SimpleEntity( 2, "se2" );
+			session.persist( se2 );
+			var se3 = new SimpleEntity( 3, "se3" );
+			session.persist( se3 );
+		} );
+	}
+
+	@Test
+	public void testIndexHint(SessionFactoryScope scope) {
+		final SQLStatementInspector statementInspector = scope.getCollectingStatementInspector();
+		statementInspector.clear();
+		scope.inTransaction( session -> {
+			TypedQuery<Integer> query = session.createQuery( "select id from SimpleEntity where id < 3", Integer.class )
+					.addQueryHint( "parents@{FORCE_INDEX=idx,DESC}" );
+			var ignored = query.getResultList();
+		} );
+		assertThat( statementInspector.getSqlQueries().get( 0 ) ).contains(
+				" parents@{FORCE_INDEX=idx,DESC} " );
+	}
+
+	@Test
+	public void testJoinHint(SessionFactoryScope scope) {
+		final SQLStatementInspector statementInspector = scope.getCollectingStatementInspector();
+		statementInspector.clear();
+		scope.inTransaction( session -> {
+			TypedQuery<ChildEntity> query = session.createQuery(
+							"select c from SimpleEntity s join s.children c where s.id < 3",
+							ChildEntity.class
+					)
+					.addQueryHint( "haSh join" );
+			var ignored = query.getResultList();
+		} );
+		assertThat( statementInspector.getSqlQueries().get( 0 ) ).contains(
+				" hash join " );
+	}
+
+	@Test
+	public void testOuterJoinHint(SessionFactoryScope scope) {
+		final SQLStatementInspector statementInspector = scope.getCollectingStatementInspector();
+		statementInspector.clear();
+		scope.inTransaction( session -> {
+			TypedQuery<ChildEntity> query = session.createQuery(
+							"select c from SimpleEntity s left join s.children c where s.id < 3",
+							ChildEntity.class
+					)
+					.addQueryHint( "haSh join" );
+			var ignored = query.getResultList();
+		} );
+		assertThat( statementInspector.getSqlQueries().get( 0 ) ).contains(
+				" hash join " );
+	}
+}
+
+@Entity
+@Table(name = "children")
+class ChildEntity {
+	@Id
+	private Integer id;
+
+	private String childName;
+
+	@ManyToOne
+	@JoinColumn(name = "parent_id", nullable = false)
+	private SimpleEntity parent;
+
+	public ChildEntity() {
+	}
+
+	public ChildEntity(String childName) {
+		this.childName = childName;
+	}
+
+	public Integer getId() {
+		return id;
+	}
+
+	public void setId(Integer id) {
+		this.id = id;
+	}
+
+	public SimpleEntity getParent() {
+		return parent;
+	}
+}
+
+@Entity(name = "SimpleEntity")
+@Table(name = "parents", indexes = { @Index(name = "idx", columnList = "id") })
+class SimpleEntity {
+	@Id
+	private Integer id;
+
+	private String name;
+
+	@OneToMany(mappedBy = "parent")
+	private Set<ChildEntity> children;
+
+	public SimpleEntity() {
+	}
+
+	public SimpleEntity(Integer id, String name) {
+		this.id = id;
+		this.name = name;
+		this.children = new HashSet<>();
+	}
+
+	public Integer getId() {
+		return id;
+	}
+
+	public void setId(Integer id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+
+	public Set<ChildEntity> getChildren() {
+		return children;
+	}
+
+	public void setChildren(Set<ChildEntity> children) {
+		this.children = children;
+	}
+
+	public void addChild(ChildEntity child) {
+		this.children.add( child );
+	}
+}