From fc1b8fdfb8a3070fb54703f741bbd0661f5796af Mon Sep 17 00:00:00 2001
From: rachithrr <rachith.ramaswamy@molecula.com>
Date: Thu, 12 Jan 2023 18:01:06 -0500
Subject: [PATCH] FB-1827: Implement Len() (#2406)

(cherry picked from commit f99be656dfdab0cfda3b34d74afa12e6b511d83d)
---
 sql3/planner/expression.go              |  2 ++
 sql3/planner/expressionanalyzercall.go  |  2 ++
 sql3/planner/inbuiltfunctionsstring.go  | 32 ++++++++++++++++++++
 sql3/test/defs/defs_string_functions.go | 39 +++++++++++++++++++++++++
 4 files changed, 75 insertions(+)

diff --git a/sql3/planner/expression.go b/sql3/planner/expression.go
index e0ad68c1f..2253719a0 100644
--- a/sql3/planner/expression.go
+++ b/sql3/planner/expression.go
@@ -1516,6 +1516,8 @@ func (n *callPlanExpression) Evaluate(currentRow []interface{}) (interface{}, er
 		return n.EvaluatePrefix(currentRow)
 	case "SPACE":
 		return n.EvaluateSpace(currentRow)
+	case "LEN":
+		return n.EvaluateLen(currentRow)
 	default:
 		return nil, sql3.NewErrInternalf("unhandled function name '%s'", n.name)
 	}
diff --git a/sql3/planner/expressionanalyzercall.go b/sql3/planner/expressionanalyzercall.go
index a2b6d04b1..1b743b913 100644
--- a/sql3/planner/expressionanalyzercall.go
+++ b/sql3/planner/expressionanalyzercall.go
@@ -269,6 +269,8 @@ func (p *ExecutionPlanner) analyzeCallExpression(call *parser.Call, scope parser
 		return p.analyseFunctionPrefixSuffix(call, scope)
 	case "SPACE":
 		return p.analyseFunctionSpace(call, scope)
+	case "LEN":
+		return p.analyseFunctionLen(call, scope)
 	default:
 		return nil, sql3.NewErrCallUnknownFunction(call.Name.NamePos.Line, call.Name.NamePos.Column, call.Name.Name)
 	}
diff --git a/sql3/planner/inbuiltfunctionsstring.go b/sql3/planner/inbuiltfunctionsstring.go
index fda45b18d..52bb71e28 100644
--- a/sql3/planner/inbuiltfunctionsstring.go
+++ b/sql3/planner/inbuiltfunctionsstring.go
@@ -195,6 +195,18 @@ func (p *ExecutionPlanner) analyseFunctionSpace(call *parser.Call, scope parser.
 	return call, nil
 }
 
+func (p *ExecutionPlanner) analyseFunctionLen(call *parser.Call, scope parser.Statement) (parser.Expr, error) {
+	if len(call.Args) != 1 {
+		return nil, sql3.NewErrCallParameterCountMismatch(call.Rparen.Line, call.Rparen.Column, call.Name.Name, 1, len(call.Args))
+	}
+
+	if !typeIsString(call.Args[0].DataType()) && !typeIsVoid(call.Args[0].DataType()) {
+		return nil, sql3.NewErrStringExpressionExpected(call.Args[0].Pos().Line, call.Args[0].Pos().Column)
+	}
+	call.ResultDataType = parser.NewDataTypeInt()
+	return call, nil
+}
+
 // reverses the string
 func (n *callPlanExpression) EvaluateReverse(currentRow []interface{}) (interface{}, error) {
 	argEval, err := n.args[0].Evaluate(currentRow)
@@ -264,6 +276,10 @@ func (n *callPlanExpression) EvaluateChar(currentRow []interface{}) (interface{}
 	if !ok {
 		return 0, sql3.NewErrInternalf("unexpected type converion %T", argEval)
 	}
+	// ascii range is [0-255]
+	if intArg < 0 || intArg > 255 {
+		return nil, sql3.NewErrValueOutOfRange(0, 0, intArg)
+	}
 
 	// Return the character that corresponds to the integer value
 	return string(rune(intArg)), nil
@@ -580,3 +596,19 @@ func (n *callPlanExpression) EvaluateSpace(currentRow []interface{}) (interface{
 	}
 	return spaces, nil
 }
+
+func (n *callPlanExpression) EvaluateLen(currentRow []interface{}) (interface{}, error) {
+	argEval, err := n.args[0].Evaluate(currentRow)
+	if err != nil {
+		return nil, err
+	}
+	if argEval == nil {
+		return nil, nil
+	}
+	stringArg, ok := argEval.(string)
+	if !ok {
+		return nil, sql3.NewErrInternalf("unexpected type converion %T", argEval)
+	}
+
+	return int64(len([]rune(stringArg))), nil
+}
diff --git a/sql3/test/defs/defs_string_functions.go b/sql3/test/defs/defs_string_functions.go
index 1790fd8e4..54529285f 100644
--- a/sql3/test/defs/defs_string_functions.go
+++ b/sql3/test/defs/defs_string_functions.go
@@ -727,5 +727,44 @@ var stringScalarFunctionsTests = TableTest{
 			),
 			Compare: CompareExactOrdered,
 		},
+		{
+			name: "LenNull",
+			SQLs: sqls(
+				"select len(null)",
+			),
+			ExpHdrs: hdrs(
+				hdr("", fldTypeInt),
+			),
+			ExpRows: rows(
+				row(nil),
+			),
+			Compare: CompareExactOrdered,
+		},
+		{
+			name: "LenString",
+			SQLs: sqls(
+				"select len(' length  ')",
+			),
+			ExpHdrs: hdrs(
+				hdr("", fldTypeInt),
+			),
+			ExpRows: rows(
+				row(int64(9)),
+			),
+			Compare: CompareExactOrdered,
+		},
+		{
+			name: "LenChar",
+			SQLs: sqls(
+				"select len(char(114))",
+			),
+			ExpHdrs: hdrs(
+				hdr("", fldTypeInt),
+			),
+			ExpRows: rows(
+				row(int64(1)),
+			),
+			Compare: CompareExactOrdered,
+		},
 	},
 }