Add new config for csv column explicit type conversion (#4781)

plugins/parsers/csv/README.md

@@ -27,6 +27,11 @@ values.
   ## If `csv_header_row_count` is set to 0, this config must be used
   csv_column_names = []
 
+  ## For assigning explicit data types to columns.
+  ## Supported types: "int", "float", "bool", "string".
+  ## If this is not specified, type conversion will be done on the types above.
+  csv_column_types = []
+
   ## Indicates the number of rows to skip before looking for header information.
   csv_skip_rows = 0
 

plugins/parsers/csv/parser.go

@@ -21,6 +21,7 @@ type Parser struct {
 	Comment           string
 	TrimSpace         bool
 	ColumnNames       []string
+	ColumnTypes       []string
 	TagColumns        []string
 	MeasurementColumn string
 	TimestampColumn   string
@@ -148,6 +149,40 @@ outer:
 				}
 			}
 
+			// Try explicit conversion only when column types is defined.
+			if len(p.ColumnTypes) > 0 {
+				// Throw error if current column count exceeds defined types.
+				if i >= len(p.ColumnTypes) {
+					return nil, fmt.Errorf("column type: column count exceeded")
+				}
+
+				var val interface{}
+				var err error
+
+				switch p.ColumnTypes[i] {
+				case "int":
+					val, err = strconv.ParseInt(value, 10, 64)
+					if err != nil {
+						return nil, fmt.Errorf("column type: parse int error %s", err)
+					}
+				case "float":
+					val, err = strconv.ParseFloat(value, 64)
+					if err != nil {
+						return nil, fmt.Errorf("column type: parse float error %s", err)
+					}
+				case "bool":
+					val, err = strconv.ParseBool(value)
+					if err != nil {
+						return nil, fmt.Errorf("column type: parse bool error %s", err)
+					}
+				default:
+					val = value
+				}
+
+				recordFields[fieldName] = val
+				continue
+			}
+
 			// attempt type conversions
 			if iValue, err := strconv.ParseInt(value, 10, 64); err == nil {
 				recordFields[fieldName] = iValue

plugins/parsers/csv/parser_test.go

@@ -147,6 +147,18 @@ func TestValueConversion(t *testing.T) {
 
 	//deep equal fields
 	require.Equal(t, expectedMetric.Fields(), returnedMetric.Fields())
+
+	// Test explicit type conversion.
+	p.ColumnTypes = []string{"float", "int", "bool", "string"}
+
+	metrics, err = p.Parse([]byte(testCSV))
+	require.NoError(t, err)
+
+	returnedMetric, err2 = metric.New(metrics[0].Name(), metrics[0].Tags(), metrics[0].Fields(), time.Unix(0, 0))
+	require.NoError(t, err2)
+
+	//deep equal fields
+	require.Equal(t, expectedMetric.Fields(), returnedMetric.Fields())
 }
 
 func TestSkipComment(t *testing.T) {