LowCardinality type dataparser support.

README.md

@@ -34,6 +34,7 @@ http://user:password@host:8123/clicks?read_timeout=10&write_timeout=20
 * Date
 * DateTime
 * Enum
+* LowCardinality(T)
 * [Array(T) (one-dimensional)](https://clickhouse.yandex/reference_en.html#Array(T))
 * [Nested(Name1 Type1, Name2 Type2, ...)](https://clickhouse.yandex/docs/en/data_types/nested_data_structures/nested/)
 

dataparser.go

@@ -230,6 +230,18 @@ func (p *arrayParser) Parse(s io.RuneScanner) (driver.Value, error) {
 	return slice.Interface(), nil
 }
 
+type lowCardinalityParser struct {
+	arg DataParser
+}
+
+func (p *lowCardinalityParser) Type() reflect.Type {
+	return p.arg.Type()
+}
+
+func (p *lowCardinalityParser) Parse(s io.RuneScanner) (driver.Value, error) {
+	return p.arg.Parse(s)
+}
+
 func newDateTimeParser(format, locname string, unquote bool) (DataParser, error) {
 	loc, err := time.LoadLocation(locname)
 	if err != nil {
@@ -431,6 +443,15 @@ func newDataParser(t *TypeDesc, unquote bool) (DataParser, error) {
 			subParsers[i] = subParser
 		}
 		return &tupleParser{subParsers}, nil
+	case "LowCardinality":
+		if len(t.Args) != 1 {
+			return nil, fmt.Errorf("element type not specified for LowCardinality")
+		}
+		subParser, err := newDataParser(t.Args[0], unquote)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create parser for LowCardinality elements: %v", err)
+		}
+		return &lowCardinalityParser{subParser}, nil
 	default:
 		return nil, fmt.Errorf("type %s is not supported", t.Name)
 	}

dataparser_test.go

@@ -253,6 +253,30 @@ func TestParseData(t *testing.T) {
 			inputdata:     "(1,2",
 			failParseData: true,
 		},
+		{
+			name:      "low cardinality string",
+			inputtype: "LowCardinality(String)",
+			inputdata: "hello",
+			output:    "hello",
+		},
+		{
+			name:      "low cardinality string with escaping",
+			inputtype: "LowCardinality(String)",
+			inputdata: `hello \'world`,
+			output:    "hello 'world",
+		},
+		{
+			name:          "low cardinality string with incorrect escaping",
+			inputtype:     "LowCardinality(String)",
+			inputdata:     `hello world\`,
+			failParseData: true,
+		},
+		{
+			name:      "low cardinality UInt64",
+			inputtype: "LowCardinality(UInt64)",
+			inputdata: "123",
+			output:    uint64(123),
+		},
 	}
 
 	for _, tc := range testCases {