HHH-16174 support for extract(epoch from ...) in HQL

documentation/src/main/asciidoc/userguide/chapters/query/hql/QueryLanguage.adoc

@@ -814,7 +814,7 @@ There are two very important function for working with dates and times.
 
 The special function `extract()` obtains a single field of a date, time, or datetime.
 
-Field types include: `day`, `month`, `year`, `second`, `minute`, `hour`, `day of week`, `day of month`, `week of year`, `date`, `time` and more.
+Field types include: `day`, `month`, `year`, `second`, `minute`, `hour`, `day of week`, `day of month`, `week of year`, `date`, `time`, `epoch` and more.
 For a full list of field types, see the Javadoc for https://docs.jboss.org/hibernate/orm/{majorMinorVersion}/javadocs/org/hibernate/query/TemporalUnit.html[`TemporalUnit`].
 
 ====

hibernate-core/src/main/antlr/org/hibernate/grammars/hql/HqlLexer.g4

@@ -181,6 +181,7 @@ ELSE				: [eE] [lL] [sS] [eE];
 EMPTY				: [eE] [mM] [pP] [tT] [yY];
 END					: [eE] [nN] [dD];
 ENTRY				: [eE] [nN] [tT] [rR] [yY];
+EPOCH				: [eE] [pP] [oO] [cC] [hH];
 ERROR				: [eE] [rR] [rR] [oO] [rR];
 ESCAPE				: [eE] [sS] [cC] [aA] [pP] [eE];
 EVERY				: [eE] [vV] [eE] [rR] [yY];

hibernate-core/src/main/antlr/org/hibernate/grammars/hql/HqlParser.g4

@@ -1473,6 +1473,7 @@ datetimeField
 	| MINUTE
 	| SECOND
 	| NANOSECOND
+	| EPOCH
 	;
 
 dayField
@@ -1577,6 +1578,7 @@ rollup
 	| EMPTY
 	| END
 	| ENTRY
+	| EPOCH
 	| ERROR
 	| ESCAPE
 	| EVERY

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

@@ -368,6 +368,8 @@ public class DerbyDialect extends Dialect {
 				return "(({fn timestampdiff(sql_tsi_day,date(char(year(?2),4)||'-01-01'),{fn timestampadd(sql_tsi_day,{fn timestampdiff(sql_tsi_day,{d '1753-01-01'},?2)}/7*7,{d '1753-01-04'})})}+7)/7)";
 			case QUARTER:
 				return "((month(?2)+2)/3)";
+			case EPOCH:
+				return "{fn timestampdiff(sql_tsi_second,{ts '1970-01-01 00:00:00'},?2)}";
 			default:
 				return "?1(?2)";
 		}

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

@@ -319,6 +319,16 @@ public class HSQLDialect extends Dialect {
 		return pattern.toString();
 	}
 
+	@Override
+	public String extractPattern(TemporalUnit unit) {
+		if ( unit == TemporalUnit.EPOCH ) {
+			return "unix_timestamp(?2)";
+		}
+		else {
+			return super.extractPattern(unit);
+		}
+	}
+
 	@Override
 	public boolean supportsDistinctFromPredicate() {
 		return true;

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

@@ -745,6 +745,8 @@ public class MySQLDialect extends Dialect {
 			case DAY_OF_YEAR:
 				return "dayofyear(?2)";
 			//TODO: case WEEK_YEAR: yearweek(?2, 3)/100
+			case EPOCH:
+				return "unix_timestamp(?2)";
 			default:
 				return "?1(?2)";
 		}

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

@@ -480,6 +480,8 @@ public class OracleDialect extends Dialect {
 				return "to_number(to_char(?2,'MI'))";
 			case SECOND:
 				return "to_number(to_char(?2,'SS'))";
+			case EPOCH:
+				return "trunc((cast(?2 at time zone 'UTC' as date) - date '1970-1-1')*86400)";
 			default:
 				return super.extractPattern(unit);
 		}

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

@@ -753,6 +753,8 @@ public class SQLServerDialect extends AbstractTransactSQLDialect {
 			case SECOND:
 				//this should evaluate to a floating point type
 				return "(datepart(second,?2)+datepart(nanosecond,?2)/1e9)";
+			case EPOCH:
+				return "datediff_big(second, '1970-01-01', ?2)";
 			default:
 				return "datepart(?1,?2)";
 		}

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

@@ -300,8 +300,13 @@ public class SybaseDialect extends AbstractTransactSQLDialect {
 
 	@Override
 	public String extractPattern(TemporalUnit unit) {
-		//TODO!!
-		return "datepart(?1,?2)";
+		if ( unit == TemporalUnit.EPOCH ) {
+			return "datediff(second, '1970-01-01 00:00:00', ?2)";
+		}
+		else {
+			//TODO!!
+			return "datepart(?1,?2)";
+		}
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/query/hql/internal/SemanticQueryBuilder.java

@@ -4199,6 +4199,12 @@ public class SemanticQueryBuilder<R> extends HqlParserBaseVisitor<Object> implem
 						resolveExpressibleTypeBasic( Integer.class ),
 						nodeBuilder
 				);
+			case HqlParser.EPOCH:
+				return new SqmExtractUnit<>(
+						TemporalUnit.EPOCH,
+						resolveExpressibleTypeBasic( Long.class ),
+						nodeBuilder
+				);
 		}
 		throw new ParsingException( "Unsupported datetime field [" + ctx.getText() + "]" );
 	}

hibernate-core/src/main/java/org/hibernate/query/sqm/TemporalUnit.java

@@ -154,8 +154,7 @@ public enum TemporalUnit {
 	TIME,
 	/**
 	 * An internal value representing the Unix epoch, the elapsed
-	 * seconds since January 1, 1970. Currently not supported in
-	 * HQL.
+	 * seconds since January 1, 1970.
 	 */
 	EPOCH,
 	/**

hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/FunctionTests.java

@@ -1518,6 +1518,17 @@ public class FunctionTests {
 		);
 	}
 
+	@Test
+	public void testExtractFunctionEpoch(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					session.createQuery("select extract(epoch from local datetime)", Long.class).getSingleResult();
+					session.createQuery("select extract(epoch from offset datetime)", Long.class).getSingleResult();
+					assertThat( session.createQuery("select extract(epoch from datetime 1974-03-23 12:35)", Long.class).getSingleResult(), is(133274100L) );
+				}
+		);
+	}
+
 	@Test
 	public void testExtractFunctionWeek(SessionFactoryScope scope) {
 		scope.inTransaction(