Implement LEFT,LENGTH,LTRIM,REPLACE,REPLICATE,REVERSE,RIGHT,RTRIM,SUBSTRING,TRIM functions

parsers/models.go

@@ -91,6 +91,16 @@ const (
 	FunctionCallIn           FunctionCallType = "In"
 	FunctionCallUpper        FunctionCallType = "Upper"
 	FunctionCallLower        FunctionCallType = "Lower"
+	FunctionCallLeft         FunctionCallType = "Left"
+	FunctionCallLength       FunctionCallType = "Length"
+	FunctionCallLTrim        FunctionCallType = "LTrim"
+	FunctionCallReplace      FunctionCallType = "Replace"
+	FunctionCallReplicate    FunctionCallType = "Replicate"
+	FunctionCallReverse      FunctionCallType = "Reverse"
+	FunctionCallRight        FunctionCallType = "Right"
+	FunctionCallRTrim        FunctionCallType = "RTrim"
+	FunctionCallSubstring    FunctionCallType = "Substring"
+	FunctionCallTrim         FunctionCallType = "Trim"
 )
 
 type FunctionCall struct {

parsers/nosql/nosql.peg

@@ -107,6 +107,10 @@ func makeOrderExpression(field interface{}, order interface{}) (parsers.OrderExp
     return value, nil
 }
 
+func createFunctionCall(functionType parsers.FunctionCallType, arguments []interface{}) (parsers.FunctionCall, error) {
+    return parsers.FunctionCall{Type: functionType, Arguments: arguments}, nil
+}
+
 func joinStrings(array []interface{}) string {
     var stringsArray []string
     for _, elem := range array {
@@ -314,26 +318,76 @@ StringFunctions <- StringEqualsExpression
     / ThreeArgumentStringFunctionExpression
     / UpperExpression
     / LowerExpression
+    / LeftExpression
+    / LengthExpression
+    / LTrimExpression
+    / ReplaceExpression
+    / ReplicateExpression
+    / ReverseExpression
+    / RightExpression
+    / RTrimExpression
+    / SubstringExpression
+    / TrimExpression
 
 UpperExpression <- "UPPER"i ws "(" ex:SelectItem ")" {
-    return parsers.FunctionCall{Type: parsers.FunctionCallUpper, Arguments: []interface{}{ex}}, nil
+    return createFunctionCall(parsers.FunctionCallUpper, []interface{}{ex})
 }
 
 LowerExpression <- "LOWER"i ws "(" ex:SelectItem ")" {
-    return parsers.FunctionCall{Type: parsers.FunctionCallLower, Arguments: []interface{}{ex}}, nil
+    return createFunctionCall(parsers.FunctionCallLower, []interface{}{ex})
 }
 
 StringEqualsExpression <- StringEquals ws "(" ws ex1:SelectItem ws "," ws ex2:SelectItem ws ignoreCase:("," ws boolean:SelectItem { return boolean, nil })? ")" {
-    return parsers.FunctionCall{Type: parsers.FunctionCallStringEquals, Arguments: []interface{}{ex1, ex2, ignoreCase}}, nil
+    return createFunctionCall(parsers.FunctionCallStringEquals, []interface{}{ex1, ex2, ignoreCase})
 }
 
 ToStringExpression <- "TOSTRING"i ws "(" ws ex:SelectItem ws ")" {
-    return parsers.FunctionCall{Type: parsers.FunctionCallToString, Arguments: []interface{}{ex}}, nil
+    return createFunctionCall(parsers.FunctionCallToString, []interface{}{ex})
 }
 
 ConcatExpression <- "CONCAT"i ws "(" ws ex1:SelectItem others:(ws "," ws ex:SelectItem { return ex, nil })+ ws ")" {
     arguments := append([]interface{}{ex1}, others.([]interface{})...)
-    return parsers.FunctionCall{Type: parsers.FunctionCallConcat, Arguments: arguments}, nil
+    return createFunctionCall(parsers.FunctionCallConcat, arguments)
+}
+
+LeftExpression <- "LEFT"i ws "(" ws ex:SelectItem ws "," ws length:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallLeft, []interface{}{ex, length})
+}
+
+LengthExpression <- "LENGTH"i ws "(" ws ex:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallLength, []interface{}{ex})
+}
+
+LTrimExpression <- "LTRIM"i ws "(" ws ex:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallLTrim, []interface{}{ex})
+}
+
+ReplaceExpression <- "REPLACE"i ws "(" ws ex1:SelectItem ws "," ws ex2:SelectItem ws "," ws ex3:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallReplace, []interface{}{ex1, ex2, ex3})
+}
+
+ReplicateExpression <- "REPLICATE"i ws "(" ws ex1:SelectItem ws "," ws ex2:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallReplicate, []interface{}{ex1, ex2})
+}
+
+ReverseExpression <- "REVERSE"i ws "(" ws ex:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallReverse, []interface{}{ex})
+}
+
+RightExpression <- "RIGHT"i ws "(" ws ex:SelectItem ws "," ws length:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallRight, []interface{}{ex, length})
+}
+
+RTrimExpression <- "RTRIM"i ws "(" ws ex:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallRTrim, []interface{}{ex})
+}
+
+SubstringExpression <- "SUBSTRING"i ws "(" ws ex:SelectItem ws "," ws startPos:SelectItem ws "," ws length:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallSubstring, []interface{}{ex, startPos, length})
+}
+
+TrimExpression <- "TRIM"i ws "(" ws ex:SelectItem ws ")" {
+    return createFunctionCall(parsers.FunctionCallTrim, []interface{}{ex})
 }
 
 ThreeArgumentStringFunctionExpression <- function:ThreeArgumentStringFunction ws "(" ws ex1:SelectItem ws "," ws ex2:SelectItem ws ignoreCase:("," ws boolean:SelectItem { return boolean, nil })? ")" {

parsers/nosql/nosql_string_functions_test.go

@@ -336,4 +336,293 @@ func Test_Execute_StringFunctions(t *testing.T) {
 			},
 		)
 	})
+
+	t.Run("Should parse function LEFT()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT LEFT(c.id, 5) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallLeft,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 5,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function LENGTH()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT LENGTH(c.id) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallLength,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function LTRIM()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT LTRIM(c.id) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallLTrim,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function REPLACE()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT REPLACE(c.id, "old", "new") FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallReplace,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeString,
+										Value: "old",
+									},
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeString,
+										Value: "new",
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function REPLICATE()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT REPLICATE(c.id, 3) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallReplicate,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 3,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function REVERSE()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT REVERSE(c.id) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallReverse,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function RIGHT()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT RIGHT(c.id, 3) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallRight,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 3,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function RTRIM()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT RTRIM(c.id) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallRTrim,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function SUBSTRING()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT SUBSTRING(c.id, 1, 5) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallSubstring,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 1,
+									},
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 5,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
+
+	t.Run("Should parse function TRIM()", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT TRIM(c.id) FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Type: parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallTrim,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+		)
+	})
 }

query_executors/memory_executor/memory_executor.go

@@ -194,6 +194,26 @@ func getFieldValue(field parsers.SelectItem, queryParameters map[string]interfac
 			return strings_Upper(typedValue.Arguments, queryParameters, row)
 		case parsers.FunctionCallLower:
 			return strings_Lower(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallLeft:
+			return strings_Left(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallLength:
+			return strings_Length(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallLTrim:
+			return strings_LTrim(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallReplace:
+			return strings_Replace(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallReplicate:
+			return strings_Replicate(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallReverse:
+			return strings_Reverse(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallRight:
+			return strings_Right(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallRTrim:
+			return strings_RTrim(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallSubstring:
+			return strings_Substring(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallTrim:
+			return strings_Trim(typedValue.Arguments, queryParameters, row)
 		case parsers.FunctionCallIsDefined:
 			return typeChecking_IsDefined(typedValue.Arguments, queryParameters, row)
 		case parsers.FunctionCallIn:

query_executors/memory_executor/memory_executor_string_functions_test.go

@@ -9,9 +9,9 @@ import (
 
 func Test_Execute_StringFunctions(t *testing.T) {
 	mockData := []memoryexecutor.RowType{
-		map[string]interface{}{"id": "123", "pk": "aaa", "str": "hello", "rng_type": true},
+		map[string]interface{}{"id": "123", "pk": "aaa", "str": "hello", "rng_type": true, "str2": "   hello "},
-		map[string]interface{}{"id": "456", "pk": "bbb", "str": "world", "rng_type": 159},
+		map[string]interface{}{"id": "456", "pk": "bbb", "str": "world", "rng_type": 159, "str2": "  world   "},
-		map[string]interface{}{"id": "789", "pk": "AAA", "str": "cool world"},
+		map[string]interface{}{"id": "789", "pk": "AAA", "str": "cool world", "str2": "          cool world  "},
 	}
 
 	t.Run("Should execute function STRINGEQUALS(ex1, ex2, ignoreCase)", func(t *testing.T) {
@@ -377,4 +377,393 @@ func Test_Execute_StringFunctions(t *testing.T) {
 			},
 		)
 	})
+
+	t.Run("Should execute function LEFT()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "left",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallLeft,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 3,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "left": "hel"},
+				map[string]interface{}{"str": "world", "left": "wor"},
+				map[string]interface{}{"str": "cool world", "left": "coo"},
+			},
+		)
+	})
+
+	t.Run("Should execute function LENGTH()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "length",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallLength,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "length": 5},
+				map[string]interface{}{"str": "world", "length": 5},
+				map[string]interface{}{"str": "cool world", "length": 10},
+			},
+		)
+	})
+
+	t.Run("Should execute function LTRIM()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "ltrimmed",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallLTrim,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str2"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "ltrimmed": "hello "},
+				map[string]interface{}{"str": "world", "ltrimmed": "world   "},
+				map[string]interface{}{"str": "cool world", "ltrimmed": "cool world  "},
+			},
+		)
+	})
+
+	t.Run("Should execute function REPLACE()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "replaced",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallReplace,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeString,
+										Value: "world",
+									},
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeString,
+										Value: "universe",
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "replaced": "hello"},
+				map[string]interface{}{"str": "world", "replaced": "universe"},
+				map[string]interface{}{"str": "cool world", "replaced": "cool universe"},
+			},
+		)
+	})
+
+	t.Run("Should execute function REPLICATE()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "replicated",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallReplicate,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 3,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "replicated": "hellohellohello"},
+				map[string]interface{}{"str": "world", "replicated": "worldworldworld"},
+				map[string]interface{}{"str": "cool world", "replicated": "cool worldcool worldcool world"},
+			},
+		)
+	})
+
+	t.Run("Should execute function REVERSE()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "reversed",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallReverse,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "reversed": "olleh"},
+				map[string]interface{}{"str": "world", "reversed": "dlrow"},
+				map[string]interface{}{"str": "cool world", "reversed": "dlrow looc"},
+			},
+		)
+	})
+
+	t.Run("Should execute function RIGHT()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "right",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallRight,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 3,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "right": "llo"},
+				map[string]interface{}{"str": "world", "right": "rld"},
+				map[string]interface{}{"str": "cool world", "right": "rld"},
+			},
+		)
+	})
+
+	t.Run("Should execute function RTRIM()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "rtrimmed",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallRTrim,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str2"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "rtrimmed": "   hello"},
+				map[string]interface{}{"str": "world", "rtrimmed": "  world"},
+				map[string]interface{}{"str": "cool world", "rtrimmed": "          cool world"},
+			},
+		)
+	})
+
+	t.Run("Should execute function SUBSTRING()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "substring",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallSubstring,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 2,
+									},
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeInteger,
+										Value: 4,
+									},
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "substring": "llo"},
+				map[string]interface{}{"str": "world", "substring": "rld"},
+				map[string]interface{}{"str": "cool world", "substring": "ol w"},
+			},
+		)
+	})
+
+	t.Run("Should execute function TRIM()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Path: []string{"c", "str"},
+						Type: parsers.SelectItemTypeField,
+					},
+					{
+						Alias: "trimmed",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallTrim,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "str2"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"str": "hello", "trimmed": "hello"},
+				map[string]interface{}{"str": "world", "trimmed": "world"},
+				map[string]interface{}{"str": "cool world", "trimmed": "cool world"},
+			},
+		)
+	})
 }

query_executors/memory_executor/string_functions.go

@@ -111,6 +111,139 @@ func strings_Lower(arguments []interface{}, queryParameters map[string]interface
 	return strings.ToLower(convertToString(value))
 }
 
+func strings_Left(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	var ok bool
+	var length int
+	str := parseString(arguments[0], queryParameters, row)
+	lengthEx := getFieldValue(arguments[1].(parsers.SelectItem), queryParameters, row)
+
+	if length, ok = lengthEx.(int); !ok {
+		fmt.Println("strings_Left - got parameters of wrong type")
+		return ""
+	}
+
+	if length <= 0 {
+		return ""
+	}
+
+	if len(str) <= length {
+		return str
+	}
+
+	return str[:length]
+}
+
+func strings_Length(arguments []interface{}, queryParameters map[string]interface{}, row RowType) int {
+	str := parseString(arguments[0], queryParameters, row)
+	return len(str)
+}
+
+func strings_LTrim(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	str := parseString(arguments[0], queryParameters, row)
+	return strings.TrimLeft(str, " ")
+}
+
+func strings_Replace(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	str := parseString(arguments[0], queryParameters, row)
+	oldStr := parseString(arguments[1], queryParameters, row)
+	newStr := parseString(arguments[2], queryParameters, row)
+	return strings.Replace(str, oldStr, newStr, -1)
+}
+
+func strings_Replicate(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	var ok bool
+	var times int
+	str := parseString(arguments[0], queryParameters, row)
+	timesEx := getFieldValue(arguments[1].(parsers.SelectItem), queryParameters, row)
+
+	if times, ok = timesEx.(int); !ok {
+		fmt.Println("strings_Replicate - got parameters of wrong type")
+		return ""
+	}
+
+	if times <= 0 {
+		return ""
+	}
+
+	if len(str) <= times {
+		return str
+	}
+
+	return strings.Repeat(str, times)
+}
+
+func strings_Reverse(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	str := parseString(arguments[0], queryParameters, row)
+	runes := []rune(str)
+
+	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
+		runes[i], runes[j] = runes[j], runes[i]
+	}
+
+	return string(runes)
+}
+
+func strings_Right(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	var ok bool
+	var length int
+	str := parseString(arguments[0], queryParameters, row)
+	lengthEx := getFieldValue(arguments[1].(parsers.SelectItem), queryParameters, row)
+
+	if length, ok = lengthEx.(int); !ok {
+		fmt.Println("strings_Right - got parameters of wrong type")
+		return ""
+	}
+
+	if length <= 0 {
+		return ""
+	}
+
+	if len(str) <= length {
+		return str
+	}
+
+	return str[len(str)-length:]
+}
+
+func strings_RTrim(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	str := parseString(arguments[0], queryParameters, row)
+	return strings.TrimRight(str, " ")
+}
+
+func strings_Substring(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	var ok bool
+	var startPos int
+	var length int
+	str := parseString(arguments[0], queryParameters, row)
+	startPosEx := getFieldValue(arguments[1].(parsers.SelectItem), queryParameters, row)
+	lengthEx := getFieldValue(arguments[2].(parsers.SelectItem), queryParameters, row)
+
+	if startPos, ok = startPosEx.(int); !ok {
+		fmt.Println("strings_Substring - got start parameters of wrong type")
+		return ""
+	}
+	if length, ok = lengthEx.(int); !ok {
+		fmt.Println("strings_Substring - got length parameters of wrong type")
+		return ""
+	}
+
+	if startPos >= len(str) {
+		return ""
+	}
+
+	endPos := startPos + length
+	if endPos > len(str) {
+		endPos = len(str)
+	}
+
+	return str[startPos:endPos]
+}
+
+func strings_Trim(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	str := parseString(arguments[0], queryParameters, row)
+	return strings.TrimSpace(str)
+}
+
 func getBoolFlag(arguments []interface{}, queryParameters map[string]interface{}, row RowType) bool {
 	ignoreCase := false
 	if len(arguments) > 2 && arguments[2] != nil {