Fix query interval definitions for date add/sub

pkg/ql/ast_nodes.go

@@ -236,7 +236,10 @@ func (n interval) ToAST() (out *ASTNode) {
 	return &ASTNode{
 		Ref: "interval",
 		Args: ASTNodeSet{
-			{Symbol: n.unit},
+			// @todo consider introducing a new concept on the ASTNode to cover
+			//       system defined symbols/keywords. This is a temporary solutions
+			//       to fix reporting interval definitions; it should eventually be reworked
+			{Value: MakeValueOf("String", n.unit)},
 			{Value: MakeValueOf("Number", n.value)},
 		},
 	}

store/adapters/rdbms/dal/iterator.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"database/sql"
 	"fmt"
+
 	"github.com/cortezaproject/corteza-server/pkg/errors"
 
 	"github.com/cortezaproject/corteza-server/pkg/dal"

store/adapters/rdbms/drivers/postgres/ql.go

@@ -63,17 +63,41 @@ var (
 			},
 		},
 
+		"interval": {
+			Handler: func(args ...exp.Expression) exp.Expression {
+				// The problem here is that PGSQL, to my findings, doesn't have functions to add/sub dates
+				// like MySQL for example.
+				//
+				// We need to construct an expression in the lines of `INTERVAL 'N UNIT'` which
+				// then becomes, for example, d + INTERVAL 'N UNIT'.
+				//
+				// The problem #2 is that we can't just use value placeholders in string literals
+				// nor is there a 2 arg function to make an interval. There is a make_interval function
+				// but that one won't do.
+				//
+				// So...
+				// (?  || 'S') makes the interval label a plural because MySQL uses singular and that
+				// is what QL supports. PgSQL uses plural, such as years, months, and days.
+				//
+				// The rest of the expression is just to construct the string which can then be casted to INTERVAL
+				// which can then be used in date math, which is done with regular math operators.
+				return exp.NewLiteralExpression("(?::INTEGER || ' ' || (?  || 'S'))::INTERVAL", args[1], args[0])
+			},
+		},
+
+		"date_add": {
+			Handler: func(args ...exp.Expression) exp.Expression {
+				return exp.NewLiteralExpression("(? + ?)", args[0], args[1])
+			},
+		},
+
+		"date_sub": {
+			Handler: func(args ...exp.Expression) exp.Expression {
+				return exp.NewLiteralExpression("(? - ?)", args[0], args[1])
+			},
+		},
+
 		// functions currently unsupported in PostgreSQL store backend
-		//"DATE_ADD": {
-		//	Handler: func(args ...exp.Expression) exp.Expression {
-		//		return exp.NewLiteralExpression("")
-		//	},
-		//},
-		//"DATE_SUB": {
-		//	Handler: func(args ...exp.Expression) exp.Expression {
-		//		return exp.NewLiteralExpression("")
-		//	},
-		//},
 		//"STD": {
 		//	Handler: func(args ...exp.Expression) exp.Expression {
 		//		return exp.NewLiteralExpression("")

store/adapters/rdbms/ql/ref.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 
 	"github.com/cortezaproject/corteza-server/pkg/ql"
+	"github.com/doug-martin/goqu/v9"
 	"github.com/doug-martin/goqu/v9/exp"
 )
 
@@ -117,6 +118,38 @@ var (
 			},
 		},
 
+		"interval": {
+			Handler: func(args ...exp.Expression) exp.Expression {
+
+				// The problem here is similar to the one with PgSQL... but more complicated...
+				// The interval duration identifiers are keywords and can't be bound via value placeholders.
+				// This forces us to interpolate the thing when building the literal expression below.
+				//
+				// Since goqu doesn't let me get the raw value of the expression... I was forced
+				// to do this calamity
+				_, aa, err := goqu.Select(args[0]).ToSQL()
+				if err != nil {
+					// This error should never occur
+					panic(err)
+				}
+				intv := aa[0].(string)
+
+				return exp.NewLiteralExpression(fmt.Sprintf("INTERVAL ? %s", intv), args[1])
+			},
+		},
+
+		"date_add": {
+			Handler: func(args ...exp.Expression) exp.Expression {
+				return exp.NewSQLFunctionExpression("DATE_ADD", args[0], args[1])
+			},
+		},
+
+		"date_sub": {
+			Handler: func(args ...exp.Expression) exp.Expression {
+				return exp.NewSQLFunctionExpression("DATE_SUB", args[0], args[1])
+			},
+		},
+
 		// @todo better negation?
 		"like": {
 			Handler: func(args ...exp.Expression) exp.Expression {