Add postgres interval cast.

postgres/cast.go

@@ -2,8 +2,9 @@ package postgres
 
 import (
 	"fmt"
-	"github.com/go-jet/jet/internal/jet"
 	"strconv"
+
+	"github.com/go-jet/jet/internal/jet"
 )
 
 type cast interface {
@@ -32,7 +33,7 @@ type cast interface {
 	AS_TIME() TimeExpression
 	// Cast expression AS text type
 	AS_TEXT() StringExpression
-
+	// Cast expression AS bytea type
 	AS_BYTEA() StringExpression
 	// Cast expression AS time with time timezone type
 	AS_TIMEZ() TimezExpression
@@ -40,6 +41,8 @@ type cast interface {
 	AS_TIMESTAMP() TimestampExpression
 	// Cast expression AS timestamp with timezone type
 	AS_TIMESTAMPZ() TimestampzExpression
+	// Cast expression AS interval type
+	AS_INTERVAL() IntervalExpression
 }
 
 type castImpl struct {
@@ -151,3 +154,8 @@ func (b *castImpl) AS_TIMESTAMP() TimestampExpression {
 func (b *castImpl) AS_TIMESTAMPZ() TimestampzExpression {
 	return TimestampzExp(b.AS("timestamp with time zone"))
 }
+
+// Cast expression AS interval type
+func (b *castImpl) AS_INTERVAL() IntervalExpression {
+	return IntervalExp(b.AS("interval"))
+}

postgres/cast_test.go

@@ -62,3 +62,10 @@ func TestExpressionCAST_AS_TIMESTAMP(t *testing.T) {
 func TestExpressionCAST_AS_TIMESTAMPZ(t *testing.T) {
 	assertSerialize(t, CAST(table2Col3).AS_TIMESTAMPZ(), "table2.col3::timestamp with time zone")
 }
+
+func TestExpressionCAST_AS_INTERVAL(t *testing.T) {
+	assertSerialize(t, CAST(table2ColTimez).AS_INTERVAL(), "table2.col_timez::interval")
+	assertSerialize(t, CAST(Time(20, 11, 10)).AS_INTERVAL(), "$1::time without time zone::interval", "20:11:10")
+	assertSerialize(t, table2ColDate.SUB(CAST(Time(20, 11, 10)).AS_INTERVAL()),
+		"(table2.col_date - $1::time without time zone::interval)", "20:11:10")
+}

postgres/interval.go

@@ -129,3 +129,22 @@ func unitToString(unit quantityAndUnit) string {
 		panic("jet: invalid INTERVAL unit type")
 	}
 }
+
+//---------------------------------------------------//
+
+type intervalWrapper struct {
+	jet.IsInterval
+	Expression
+}
+
+func newIntervalExpressionWrap(expression Expression) IntervalExpression {
+	intervalWrap := intervalWrapper{Expression: expression}
+	return &intervalWrap
+}
+
+// IntervalExp is interval expression wrapper around arbitrary expression.
+// Allows go compiler to see any expression as interval expression.
+// Does not add sql cast to generated sql builder output.
+func IntervalExp(expression Expression) IntervalExpression {
+	return newIntervalExpressionWrap(expression)
+}