Add support for PostgreSQL interval column

internal/jet/utils_test.go

@@ -0,0 +1,19 @@
+package jet
+
+import (
+	"gotest.tools/assert"
+	"testing"
+)
+
+func TestOptionalOrDefaultString(t *testing.T) {
+	assert.Equal(t, OptionalOrDefaultString("default"), "default")
+	assert.Equal(t, OptionalOrDefaultString("default", "optional"), "optional")
+}
+
+func TestOptionalOrDefaultExpression(t *testing.T) {
+	defaultExpression := table2ColFloat
+	optionalExpression := table1Col1
+
+	assert.Equal(t, OptionalOrDefaultExpression(defaultExpression), defaultExpression)
+	assert.Equal(t, OptionalOrDefaultExpression(defaultExpression, optionalExpression), optionalExpression)
+}