lightning/parser: support STARTING BY

br/pkg/lightning/config/config.go

@@ -455,6 +455,9 @@ type CSVConfig struct {
 	TrimLastSep     bool   `toml:"trim-last-separator" json:"trim-last-separator"`
 	NotNull         bool   `toml:"not-null" json:"not-null"`
 	BackslashEscape bool   `toml:"backslash-escape" json:"backslash-escape"`
+	// hide these options for lightning configuration file, they can only be used by LOAD DATA
+	// https://dev.mysql.com/doc/refman/8.0/en/load-data.html#load-data-field-line-handling
+	StartingBy string `toml:"-" json:"-"`
 }
 
 type MydumperRuntime struct {

br/pkg/lightning/mydump/csv_parser.go

@@ -47,9 +47,10 @@ type CSVParser struct {
 	blockParser
 	cfg *config.CSVConfig
 
-	comma   []byte
-	quote   []byte
-	newLine []byte
+	comma      []byte
+	quote      []byte
+	newLine    []byte
+	startingBy []byte
 
 	charsetConvertor *CharsetConvertor
 	// These variables are used with IndexAnyByte to search a byte slice for the
@@ -120,6 +121,12 @@ func NewCSVParser(
 	}
 	unquoteStopSet = append(unquoteStopSet, newLineStopSet...)
 
+	if len(cfg.StartingBy) > 0 {
+		if strings.Contains(cfg.StartingBy, terminator) {
+			return nil, errors.New("starting-by cannot contain (line) terminator")
+		}
+	}
+
 	escFlavor := backslashEscapeFlavorNone
 	if cfg.BackslashEscape {
 		escFlavor = backslashEscapeFlavorMySQL
@@ -138,6 +145,7 @@ func NewCSVParser(
 		comma:             []byte(separator),
 		quote:             []byte(delimiter),
 		newLine:           []byte(terminator),
+		startingBy:        []byte(cfg.StartingBy),
 		escFlavor:         escFlavor,
 		quoteByteSet:      makeByteSet(quoteStopSet),
 		unquoteByteSet:    makeByteSet(unquoteStopSet),
@@ -370,11 +378,43 @@ func (parser *CSVParser) readRecord(dst []string) ([]string, error) {
 
 	isEmptyLine := true
 	whitespaceLine := true
+	foundStartingByThisLine := false
 	prevToken := csvTokenNewLine
 	var firstToken csvToken
 
 outside:
 	for {
+		// we should drop
+		// 1. the whole line if it does not contain startingBy
+		// 2. any character before startingBy
+		// since we have checked startingBy does not contain terminator, we can
+		// split at terminator to check the substring contains startingBy. Even
+		// if the terminator is inside a quoted field which means it's not the
+		// end of a line, the substring can still be dropped by rule 2.
+		if len(parser.startingBy) > 0 && !foundStartingByThisLine {
+			oldPos := parser.pos
+			content, _, err := parser.ReadUntilTerminator()
+			if err != nil {
+				if !(errors.Cause(err) == io.EOF) {
+					return nil, err
+				}
+				if len(content) == 0 {
+					return nil, err
+				}
+				// if we reached EOF, we should still check the content contains
+				// startingBy and try to put back and parse it.
+			}
+			idx := bytes.Index(content, parser.startingBy)
+			if idx == -1 {
+				continue
+			}
+			foundStartingByThisLine = true
+			content = content[idx+len(parser.startingBy):]
+			content = append(content, parser.newLine...)
+			parser.buf = append(content, parser.buf...)
+			parser.pos = oldPos + int64(idx+len(parser.startingBy))
+		}
+
 		content, firstByte, err := parser.readUntil(&parser.unquoteByteSet)
 
 		if len(content) > 0 {
@@ -415,6 +455,7 @@ outside:
 			}
 			whitespaceLine = false
 		case csvTokenNewLine:
+			foundStartingByThisLine = false
 			// new line = end of record (ignore empty lines)
 			prevToken = firstToken
 			if isEmptyLine {
@@ -578,17 +619,21 @@ func (parser *CSVParser) ReadColumns() error {
 }
 
 // ReadUntilTerminator seeks the file until the terminator token is found, and
-// returns the file offset beyond the terminator.
-// This function is used in strict-format dividing a CSV file.
-func (parser *CSVParser) ReadUntilTerminator() (int64, error) {
+// returns
+// - the content before terminator
+// - the file offset beyond the terminator
+// - error
+// Note that the terminator string pattern may be the content of a field, which
+// means it's inside quotes. Caller should make sure to handle this case.
+func (parser *CSVParser) ReadUntilTerminator() ([]byte, int64, error) {
 	for {
-		_, firstByte, err := parser.readUntil(&parser.newLineByteSet)
+		content, firstByte, err := parser.readUntil(&parser.newLineByteSet)
 		if err != nil {
-			return 0, err
+			return content, 0, err
 		}
 		parser.skipBytes(1)
 		if ok, err := parser.tryReadNewLine(firstByte); ok || err != nil {
-			return parser.pos, err
+			return content, parser.pos, err
 		}
 	}
 }

br/pkg/lightning/mydump/csv_parser_test.go

@@ -55,6 +55,35 @@ func runTestCasesCSV(t *testing.T, cfg *config.MydumperRuntime, blockBufSize int
 	}
 }
 
+func runTestCasesCSVIgnoreNLines(t *testing.T, cfg *config.MydumperRuntime, blockBufSize int64, cases []testCase, ignoreNLines int) {
+	for _, tc := range cases {
+		charsetConvertor, err := mydump.NewCharsetConvertor(cfg.DataCharacterSet, cfg.DataInvalidCharReplace)
+		assert.NoError(t, err)
+		parser, err := mydump.NewCSVParser(context.Background(), &cfg.CSV, mydump.NewStringReader(tc.input), blockBufSize, ioWorkers, false, charsetConvertor)
+		assert.NoError(t, err)
+
+		for ignoreNLines > 0 {
+			// IGNORE N LINES will directly find (line) terminator without checking it's inside quotes
+			_, _, err = parser.ReadUntilTerminator()
+			if errors.Cause(err) == io.EOF {
+				assert.Len(t, tc.expected, 0, "input = %q", tc.input)
+				return
+			}
+			assert.NoError(t, err)
+			ignoreNLines--
+		}
+
+		for i, row := range tc.expected {
+			comment := fmt.Sprintf("input = %q, row = %d", tc.input, i+1)
+			e := parser.ReadRow()
+			assert.NoErrorf(t, e, "input = %q, row = %d, error = %s", tc.input, i+1, errors.ErrorStack(e))
+			assert.Equal(t, int64(i)+1, parser.LastRow().RowID, comment)
+			assert.Equal(t, row, parser.LastRow().Row, comment)
+		}
+		assert.ErrorIsf(t, errors.Cause(parser.ReadRow()), io.EOF, "input = %q", tc.input)
+	}
+}
+
 func runFailingTestCasesCSV(t *testing.T, cfg *config.MydumperRuntime, blockBufSize int64, cases []string) {
 	for _, tc := range cases {
 		charsetConvertor, err := mydump.NewCharsetConvertor(cfg.DataCharacterSet, cfg.DataInvalidCharReplace)
@@ -935,6 +964,211 @@ func TestTerminator(t *testing.T) {
 	runTestCasesCSV(t, &cfg, 1, testCases)
 }
 
+func TestStartingBy(t *testing.T) {
+	cfg := config.MydumperRuntime{
+		CSV: config.CSVConfig{
+			Separator:  ",",
+			Delimiter:  `"`,
+			Terminator: "\n",
+			StartingBy: "xxx",
+		},
+	}
+	testCases := []testCase{
+		{
+			input: `xxx"abc",1
+something xxx"def",2
+"ghi",3`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("abc"), types.NewStringDatum("1")},
+				{types.NewStringDatum("def"), types.NewStringDatum("2")},
+			},
+		},
+	}
+	runTestCasesCSV(t, &cfg, 1, testCases)
+
+	testCases = []testCase{
+		{
+			input: `xxxabc,1
+something xxxdef,2
+ghi,3
+"bad syntax"aaa`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("abc"), types.NewStringDatum("1")},
+				{types.NewStringDatum("def"), types.NewStringDatum("2")},
+			},
+		},
+	}
+	runTestCasesCSV(t, &cfg, 1, testCases)
+
+	// test that special characters appears before StartingBy, and StartingBy only takes effect after once
+
+	testCases = []testCase{
+		{
+			input: `xxx"abc",1
+something xxxdef,2
+"ghi",3
+"yyy"xxx"yyy",4
+"yyy",5,xxxyyy,5
+qwe,zzzxxxyyy,6
+"yyyxxx"yyyxxx",7
+yyy",5,xxxxxx,8
+`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("abc"), types.NewStringDatum("1")},
+				{types.NewStringDatum("def"), types.NewStringDatum("2")},
+				{types.NewStringDatum("yyy"), types.NewStringDatum("4")},
+				{types.NewStringDatum("yyy"), types.NewStringDatum("5")},
+				{types.NewStringDatum("yyy"), types.NewStringDatum("6")},
+				{types.NewStringDatum("yyyxxx"), types.NewStringDatum("7")},
+				{types.NewStringDatum("xxx"), types.NewStringDatum("8")},
+			},
+		},
+	}
+	runTestCasesCSV(t, &cfg, 1, testCases)
+
+	// test StartingBy contains special characters
+
+	cfg = config.MydumperRuntime{
+		CSV: config.CSVConfig{
+			Separator:  ",",
+			Delimiter:  `"`,
+			Terminator: "\n",
+			StartingBy: "x,xx",
+		},
+	}
+	testCases = []testCase{
+		{
+			input: `x,xx"abc",1
+something x,xxdef,2
+"ghi",3
+"yyy"xxx"yyy",4
+"yyy",5,xxxyyy,5
+qwe,zzzxxxyyy,6
+"yyyxxx"yyyxxx",7
+yyy",5,xx,xxxx,8`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("abc"), types.NewStringDatum("1")},
+				{types.NewStringDatum("def"), types.NewStringDatum("2")},
+				{types.NewStringDatum("xx"), types.NewStringDatum("8")},
+			},
+		},
+	}
+	runTestCasesCSV(t, &cfg, 1, testCases)
+
+	cfg = config.MydumperRuntime{
+		CSV: config.CSVConfig{
+			Separator:  ",",
+			Delimiter:  `"`,
+			Terminator: "\n",
+			StartingBy: `x"xx`,
+		},
+	}
+	testCases = []testCase{
+		{
+			input: `x"xx"abc",1
+something x"xxdef,2
+"ghi",3
+"yyy"xxx"yyy",4
+"yyy",5,xxxyyy,5
+qwe,zzzxxxyyy,6
+"yyyxxx"yyyxxx",7
+yyy",5,xx"xxxx,8
+`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("abc"), types.NewStringDatum("1")},
+				{types.NewStringDatum("def"), types.NewStringDatum("2")},
+				{types.NewStringDatum("xx"), types.NewStringDatum("8")},
+			},
+		},
+	}
+	runTestCasesCSV(t, &cfg, 1, testCases)
+
+	cfg = config.MydumperRuntime{
+		CSV: config.CSVConfig{
+			Separator:  ",",
+			Delimiter:  `"`,
+			Terminator: "\n",
+			StartingBy: "x\nxx",
+		},
+	}
+	_, err := mydump.NewCSVParser(context.Background(), &cfg.CSV, nil, 1, ioWorkers, false, nil)
+	require.ErrorContains(t, err, "starting-by cannot contain (line) terminator")
+}
+
+func TestCallerCanIgnoreNLines(t *testing.T) {
+	cfg := config.MydumperRuntime{
+		CSV: config.CSVConfig{
+			Separator:  ",",
+			Delimiter:  `"`,
+			Terminator: "\n",
+		},
+	}
+	testCases := []testCase{
+		{
+			input: `1,1
+2,2
+3,3`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("3"), types.NewStringDatum("3")},
+			},
+		},
+	}
+	runTestCasesCSVIgnoreNLines(t, &cfg, 1, testCases, 2)
+
+	testCases = []testCase{
+		{
+			input: `"bad syntax"1
+"b",2
+"c",3`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("c"), types.NewStringDatum("3")},
+			},
+		},
+	}
+	runTestCasesCSVIgnoreNLines(t, &cfg, 1, testCases, 2)
+
+	cfg = config.MydumperRuntime{
+		CSV: config.CSVConfig{
+			Separator:  ",",
+			Delimiter:  `"`,
+			Terminator: "\n",
+		},
+	}
+	testCases = []testCase{
+		{
+			input: `1,1
+2,2
+3,3`,
+			expected: [][]types.Datum{},
+		},
+	}
+	runTestCasesCSVIgnoreNLines(t, &cfg, 1, testCases, 100)
+
+	// test IGNORE N LINES will directly find (line) terminator without checking it's inside quotes
+
+	cfg = config.MydumperRuntime{
+		CSV: config.CSVConfig{
+			Separator:  ",",
+			Delimiter:  `"`,
+			Terminator: "\n",
+		},
+	}
+	testCases = []testCase{
+		{
+			input: `"a
+",1
+"b
+",2
+"c",3`,
+			expected: [][]types.Datum{
+				{types.NewStringDatum("b\n"), types.NewStringDatum("2")},
+				{types.NewStringDatum("c"), types.NewStringDatum("3")},
+			},
+		},
+	}
+	runTestCasesCSVIgnoreNLines(t, &cfg, 1, testCases, 2)
+}
+
 func TestCharsetConversion(t *testing.T) {
 	cfg := config.MydumperRuntime{
 		CSV: config.CSVConfig{

br/pkg/lightning/mydump/region.go

@@ -431,7 +431,7 @@ func SplitLargeFile(
 			if err = parser.SetPos(endOffset, prevRowIDMax); err != nil {
 				return 0, nil, nil, err
 			}
-			pos, err := parser.ReadUntilTerminator()
+			_, pos, err := parser.ReadUntilTerminator()
 			if err != nil {
 				if !errors.ErrorEqual(err, io.EOF) {
 					return 0, nil, nil, err