From a4f18fb25f1dc4b35369c89c8d55ad001aafe2e4 Mon Sep 17 00:00:00 2001
From: rachithrr <rachith.ramaswamy@molecula.com>
Date: Thu, 15 Dec 2022 01:11:29 +0530
Subject: [PATCH] FB-1812: implement stringsplit() (#2362)

---
 sql3/planner/expression.go              |  2 +
 sql3/planner/expressionanalyzercall.go  |  2 +
 sql3/planner/inbuiltfunctionsstring.go  | 50 +++++++++++++++++++++++++
 sql3/test/defs/defs_string_functions.go | 26 +++++++++++++
 4 files changed, 80 insertions(+)

diff --git a/sql3/planner/expression.go b/sql3/planner/expression.go
index bf89d9f90..d41c3d670 100644
--- a/sql3/planner/expression.go
+++ b/sql3/planner/expression.go
@@ -1484,6 +1484,8 @@ func (n *callPlanExpression) Evaluate(currentRow []interface{}) (interface{}, er
 		return n.EvaluateReverse(currentRow)
 	case "UPPER":
 		return n.EvaluateUpper(currentRow)
+	case "STRINGSPLIT":
+		return n.EvaluateStringSplit(currentRow)
 	case "SUBSTRING":
 		return n.EvaluateSubstring(currentRow)
 	case "LOWER":
diff --git a/sql3/planner/expressionanalyzercall.go b/sql3/planner/expressionanalyzercall.go
index 3aa315e53..bb13fc548 100644
--- a/sql3/planner/expressionanalyzercall.go
+++ b/sql3/planner/expressionanalyzercall.go
@@ -245,6 +245,8 @@ func (p *ExecutionPlanner) analyzeCallExpression(call *parser.Call, scope parser
 		return p.analyseFunctionReverse(call, scope)
 	case "UPPER":
 		return p.analyzeFunctionUpper(call, scope)
+	case "STRINGSPLIT":
+		return p.analyseFunctionStringSplit(call, scope)
 	case "SUBSTRING":
 		return p.analyseFunctionSubstring(call, scope)
 	case "LOWER":
diff --git a/sql3/planner/inbuiltfunctionsstring.go b/sql3/planner/inbuiltfunctionsstring.go
index 24b84510e..9ad34270b 100644
--- a/sql3/planner/inbuiltfunctionsstring.go
+++ b/sql3/planner/inbuiltfunctionsstring.go
@@ -53,6 +53,29 @@ func (p *ExecutionPlanner) analyzeFunctionLower(call *parser.Call, scope parser.
 	if !typeIsString(call.Args[0].DataType()) {
 		return nil, sql3.NewErrStringExpressionExpected(call.Args[0].Pos().Line, call.Args[0].Pos().Column)
 	}
+	call.ResultDataType = parser.NewDataTypeString()
+
+	return call, nil
+}
+
+func (p *ExecutionPlanner) analyseFunctionStringSplit(call *parser.Call, scope parser.Statement) (parser.Expr, error) {
+	if len(call.Args) <= 1 || len(call.Args) > 3 {
+		return nil, sql3.NewErrCallParameterCountMismatch(call.Rparen.Line, call.Rparen.Column, call.Name.Name, 2, len(call.Args))
+	}
+
+	if !typeIsString(call.Args[0].DataType()) {
+		return nil, sql3.NewErrStringExpressionExpected(call.Args[0].Pos().Line, call.Args[0].Pos().Column)
+	}
+
+	// string seperator
+	if !typeIsString(call.Args[1].DataType()) {
+		return nil, sql3.NewErrStringExpressionExpected(call.Args[1].Pos().Line, call.Args[1].Pos().Column)
+	}
+
+	// third argument is the position. optional, defaults to 0
+	if len(call.Args) == 3 && !typeIsInteger(call.Args[2].DataType()) {
+		return nil, sql3.NewErrIntExpressionExpected(call.Args[2].Pos().Line, call.Args[2].Pos().Column)
+	}
 
 	call.ResultDataType = parser.NewDataTypeString()
 
@@ -188,6 +211,33 @@ func (n *callPlanExpression) EvaluateReplaceAll(currentRow []interface{}) (inter
 	return strings.ReplaceAll(stringArgOne, stringArgTwo, stringArgThree), nil
 }
 
+// takes a string, seperator and the position `n`, splits the string and returns n'th substring
+func (n *callPlanExpression) EvaluateStringSplit(currentRow []interface{}) (interface{}, error) {
+	inputString, err := evaluateStringArg(n.args[0], currentRow)
+	if err != nil {
+		return nil, err
+	}
+	seperator, err := evaluateStringArg(n.args[1], currentRow)
+	if err != nil {
+		return nil, err
+	}
+	if len(n.args) == 2 {
+		return strings.Split(inputString, seperator)[0], nil
+	}
+	pos, err := strconv.Atoi(n.args[2].String())
+	if err != nil {
+		return nil, sql3.NewErrInternalf("unexpected type converion %T", n.args[2])
+	}
+
+	res := strings.Split(inputString, seperator)
+	if pos <= 0 {
+		return res[0], nil
+	} else if len(res) > pos {
+		return res[pos], nil
+	}
+	return "", nil
+}
+
 func evaluateStringArg(n types.PlanExpression, currentRow []interface{}) (string, error) {
 	argOneEval, err := n.Evaluate(currentRow)
 	if err != nil {
diff --git a/sql3/test/defs/defs_string_functions.go b/sql3/test/defs/defs_string_functions.go
index b616196f2..a407e4afc 100644
--- a/sql3/test/defs/defs_string_functions.go
+++ b/sql3/test/defs/defs_string_functions.go
@@ -56,6 +56,32 @@ var stringScalarFunctionsTests = TableTest{
 			),
 			Compare: CompareExactUnordered,
 		},
+		{
+			name: "StringSplitNoPos",
+			SQLs: sqls(
+				"select stringsplit('string,split', ',')",
+			),
+			ExpHdrs: hdrs(
+				hdr("", fldTypeString),
+			),
+			ExpRows: rows(
+				row(string("string")),
+			),
+			Compare: CompareExactUnordered,
+		},
+		{
+			name: "StringSplitPos",
+			SQLs: sqls(
+				"select stringsplit('string,split,now', stringsplit(',mid,', 'mid', 1), 2)",
+			),
+			ExpHdrs: hdrs(
+				hdr("", fldTypeString),
+			),
+			ExpRows: rows(
+				row(string("now")),
+			),
+			Compare: CompareExactUnordered,
+		},
 		{
 			name: "SubstringNegativeIndex",
 			SQLs: sqls(