Merge pull request #417 from Shopify/uuid-as-id

Pagination beyond uint64

Author: driv3r

CHANGELOG.md

@@ -7,6 +7,8 @@ All notable changes to this project will be documented in this file.
 ### Added
 
 - Changelog.
+- Pagination keys beyond UINT64 @milanatshopify #417
+- Pagination keys other than UINT64 have to have binary collation @grodowski #422
 
 ## [1.1.0]
 

Makefile

@@ -1,5 +1,5 @@
 # Variables to be built into the binary
-VERSION         := 1.1.0
+VERSION         := 1.2.0
 
 # This variable can be overwritten by the caller
 DATETIME        ?= $(shell date -u +%Y%m%d%H%M%S)

batch_writer.go

@@ -56,12 +56,13 @@ func (w *BatchWriter) WriteRowBatch(batch *RowBatch) error {
 			return nil
 		}
 
-		startPaginationKeypos, err := values[0].GetUint64(batch.PaginationKeyIndex())
+		paginationColumn := batch.TableSchema().GetPaginationColumn()
+
+		startPaginationKeypos, err := NewPaginationKeyFromRow(values[0], batch.PaginationKeyIndex(), paginationColumn)
 		if err != nil {
 			return err
 		}
-
-		endPaginationKeypos, err := values[len(values)-1].GetUint64(batch.PaginationKeyIndex())
+		endPaginationKeypos, err := NewPaginationKeyFromRow(values[len(values)-1], batch.PaginationKeyIndex(), paginationColumn)
 		if err != nil {
 			return err
 		}
@@ -78,12 +79,12 @@ func (w *BatchWriter) WriteRowBatch(batch *RowBatch) error {
 
 		query, args, err := batch.AsSQLQuery(db, table)
 		if err != nil {
-			return fmt.Errorf("during generating sql query at paginationKey %v -> %v: %v", startPaginationKeypos, endPaginationKeypos, err)
+			return fmt.Errorf("during generating sql query at paginationKey %s -> %s: %v", startPaginationKeypos.String(), endPaginationKeypos.String(), err)
 		}
 
 		stmt, err := w.stmtCache.StmtFor(w.DB, query)
 		if err != nil {
-			return fmt.Errorf("during prepare query near paginationKey %v -> %v (%s): %v", startPaginationKeypos, endPaginationKeypos, query, err)
+			return fmt.Errorf("during prepare query near paginationKey %s -> %s (%s): %v", startPaginationKeypos.String(), endPaginationKeypos.String(), query, err)
 		}
 
 		tx, err := w.DB.Begin()
@@ -94,14 +95,14 @@ func (w *BatchWriter) WriteRowBatch(batch *RowBatch) error {
 		_, err = tx.Stmt(stmt).Exec(args...)
 		if err != nil {
 			tx.Rollback()
-			return fmt.Errorf("during exec query near paginationKey %v -> %v (%s): %v", startPaginationKeypos, endPaginationKeypos, query, err)
+			return fmt.Errorf("during exec query near paginationKey %s -> %s (%s): %v", startPaginationKeypos.String(), endPaginationKeypos.String(), query, err)
 		}
 
 		if w.InlineVerifier != nil {
 			mismatches, err := w.InlineVerifier.CheckFingerprintInline(tx, db, table, batch, w.EnforceInlineVerification)
 			if err != nil {
 				tx.Rollback()
-				return fmt.Errorf("during fingerprint checking for paginationKey %v -> %v (%s): %v", startPaginationKeypos, endPaginationKeypos, query, err)
+				return fmt.Errorf("during fingerprint checking for paginationKey %s -> %s (%s): %v", startPaginationKeypos.String(), endPaginationKeypos.String(), query, err)
 			}
 
 			if w.EnforceInlineVerification {
@@ -119,7 +120,7 @@ func (w *BatchWriter) WriteRowBatch(batch *RowBatch) error {
 		err = tx.Commit()
 		if err != nil {
 			tx.Rollback()
-			return fmt.Errorf("during commit near paginationKey %v -> %v (%s): %v", startPaginationKeypos, endPaginationKeypos, query, err)
+			return fmt.Errorf("during commit near paginationKey %s -> %s (%s): %v", startPaginationKeypos.String(), endPaginationKeypos.String(), query, err)
 		}
 
 		// Note that the state tracker expects us the track based on the original

compression_verifier.go

@@ -49,6 +49,7 @@ func (e UnsupportedCompressionError) Error() string {
 type CompressionVerifier struct {
 	logger *logrus.Entry
 
+	TableSchemaCache        TableSchemaCache
 	supportedAlgorithms     map[string]struct{}
 	tableColumnCompressions TableColumnCompressionConfig
 }
@@ -59,32 +60,52 @@ type CompressionVerifier struct {
 // The GetCompressedHashes method checks if the existing table contains compressed data
 // and will apply the decompression algorithm to the applicable columns if necessary.
 // After the columns are decompressed, the hashes of the data are used to verify equality
-func (c *CompressionVerifier) GetCompressedHashes(db *sql.DB, schema, table, paginationKeyColumn string, columns []schema.TableColumn, paginationKeys []uint64) (map[uint64][]byte, error) {
+func (c *CompressionVerifier) GetCompressedHashes(db *sql.DB, schemaName, tableName, paginationKeyColumn string, columns []schema.TableColumn, paginationKeys []interface{}) (map[string][]byte, error) {
 	c.logger.WithFields(logrus.Fields{
 		"tag":   "compression_verifier",
-		"table": table,
+		"table": tableName,
 	}).Info("decompressing table data before verification")
 
-	tableCompression := c.tableColumnCompressions[table]
+	tableCompression := c.tableColumnCompressions[tableName]
 
 	// Extract the raw rows using SQL to be decompressed
-	rows, err := getRows(db, schema, table, paginationKeyColumn, columns, paginationKeys)
+	rows, err := getRows(db, schemaName, tableName, paginationKeyColumn, columns, paginationKeys)
 	if err != nil {
 		return nil, err
 	}
 	defer rows.Close()
 
-	// Decompress applicable columns and hash the resulting column values for comparison
-	resultSet := make(map[uint64][]byte)
+	table := c.TableSchemaCache.Get(schemaName, tableName)
+	if table == nil {
+		return nil, fmt.Errorf("table %s.%s not found in schema cache", schemaName, tableName)
+	}
+	paginationColumn := table.GetPaginationColumn()
+	resultSet := make(map[string][]byte)
+
 	for rows.Next() {
 		rowData, err := ScanByteRow(rows, len(columns)+1)
 		if err != nil {
 			return nil, err
 		}
 
-		paginationKey, err := strconv.ParseUint(string(rowData[0]), 10, 64)
-		if err != nil {
-			return nil, err
+		var paginationKeyStr string
+		switch paginationColumn.Type {
+		case schema.TYPE_NUMBER, schema.TYPE_MEDIUM_INT:
+			paginationKeyUint, err := strconv.ParseUint(string(rowData[0]), 10, 64)
+			if err != nil {
+				return nil, err
+			}
+			paginationKeyStr = NewUint64Key(paginationKeyUint).String()
+
+		case schema.TYPE_BINARY, schema.TYPE_STRING:
+			paginationKeyStr = NewBinaryKey(rowData[0]).String()
+
+		default:
+			paginationKeyUint, err := strconv.ParseUint(string(rowData[0]), 10, 64)
+			if err != nil {
+				return nil, err
+			}
+			paginationKeyStr = NewUint64Key(paginationKeyUint).String()
 		}
 
 		// Decompress the applicable columns and then hash them together
@@ -95,7 +116,7 @@ func (c *CompressionVerifier) GetCompressedHashes(db *sql.DB, schema, table, pag
 		for idx, column := range columns {
 			if algorithm, ok := tableCompression[column.Name]; ok {
 				// rowData contains the result of "SELECT paginationKeyColumn, * FROM ...", so idx+1 to get each column
-				decompressedColData, err := c.Decompress(table, column.Name, algorithm, rowData[idx+1])
+				decompressedColData, err := c.Decompress(tableName, column.Name, algorithm, rowData[idx+1])
 				if err != nil {
 					return nil, err
 				}
@@ -111,20 +132,20 @@ func (c *CompressionVerifier) GetCompressedHashes(db *sql.DB, schema, table, pag
 			return nil, err
 		}
 
-		resultSet[paginationKey] = decompressedRowHash
+		resultSet[paginationKeyStr] = decompressedRowHash
 	}
 
 	metrics.Gauge(
 		"compression_verifier_decompress_rows",
 		float64(len(resultSet)),
-		[]MetricTag{{"table", table}},
+		[]MetricTag{{"table", tableName}},
 		1.0,
 	)
 
 	logrus.WithFields(logrus.Fields{
 		"tag":   "compression_verifier",
 		"rows":  len(resultSet),
-		"table": table,
+		"table": tableName,
 	}).Debug("decompressed rows will be compared")
 
 	return resultSet, nil
@@ -192,12 +213,13 @@ func (c *CompressionVerifier) verifyConfiguredCompression(tableColumnCompression
 
 // NewCompressionVerifier first checks the map for supported compression algorithms before
 // initializing and returning the initialized instance.
-func NewCompressionVerifier(tableColumnCompressions TableColumnCompressionConfig) (*CompressionVerifier, error) {
+func NewCompressionVerifier(tableColumnCompressions TableColumnCompressionConfig, tableSchemaCache TableSchemaCache) (*CompressionVerifier, error) {
 	supportedAlgorithms := make(map[string]struct{})
 	supportedAlgorithms[CompressionSnappy] = struct{}{}
 
 	compressionVerifier := &CompressionVerifier{
 		logger:                  logrus.WithField("tag", "compression_verifier"),
+		TableSchemaCache:        tableSchemaCache,
 		supportedAlgorithms:     supportedAlgorithms,
 		tableColumnCompressions: tableColumnCompressions,
 	}
@@ -209,7 +231,7 @@ func NewCompressionVerifier(tableColumnCompressions TableColumnCompressionConfig
 	return compressionVerifier, nil
 }
 
-func getRows(db *sql.DB, schema, table, paginationKeyColumn string, columns []schema.TableColumn, paginationKeys []uint64) (*sqlorig.Rows, error) {
+func getRows(db *sql.DB, schema, table, paginationKeyColumn string, columns []schema.TableColumn, paginationKeys []interface{}) (*sqlorig.Rows, error) {
 	quotedPaginationKey := QuoteField(paginationKeyColumn)
 	sql, args, err := rowSelector(columns, paginationKeyColumn).
 		From(QuotedTableNameFromString(schema, table)).

config.go

@@ -376,12 +376,17 @@ func (c ForceIndexConfig) IndexFor(schemaName, tableName string) string {
 // CascadingPaginationColumnConfig to configure pagination columns to be
 // used. The term `Cascading` to denote that greater specificity takes
 // precedence.
+//
+// IMPORTANT: All configured pagination columns must contain unique values.
+// When specifying a FallbackColumn for tables with composite primary keys,
+// ensure the column has a unique constraint to prevent data loss during migration.
 type CascadingPaginationColumnConfig struct {
 	// PerTable has greatest specificity and takes precedence over the other options
 	PerTable map[string]map[string]string // SchemaName => TableName => ColumnName
 
 	// FallbackColumn is a global default to fallback to and is less specific than the
-	// default, which is the Primary Key
+	// default, which is the Primary Key.
+	// This column MUST have unique values (ideally a unique constraint) for data integrity.
 	FallbackColumn string
 }
 
@@ -727,10 +732,15 @@ type Config struct {
 	//
 	ForceIndexForVerification ForceIndexConfig
 
-	// Ghostferry requires a single numeric column to paginate over tables. Inferring that column is done in the following exact order:
+	// Ghostferry requires a single numeric or binary column to paginate over tables. Inferring that column is done in the following exact order:
 	// 1. Use the PerTable pagination column, if configured for a table. Fail if we cannot find this column in the table.
-	// 2. Use the table's primary key column as the pagination column. Fail if the primary key is not numeric or is a composite key without a FallbackColumn specified.
+	// 2. Use the table's primary key column as the pagination column. Fail if the primary key is not numeric/binary or is a composite key without a FallbackColumn specified.
 	// 3. Use the FallbackColumn pagination column, if configured. Fail if we cannot find this column in the table.
+	//
+	// IMPORTANT: The pagination column MUST contain unique values for data integrity.
+	// When using a FallbackColumn (typically "id") for tables with composite primary keys, this column must have a unique constraint.
+	// The pagination algorithm uses WHERE pagination_key > last_key ORDER BY pagination_key LIMIT batch_size.
+	// If duplicate values exist, rows may be skipped during iteration, resulting in data loss during the migration.
 	CascadingPaginationColumnConfig *CascadingPaginationColumnConfig
 
 	// SkipTargetVerification is used to enable or disable target verification during moves.

cursor.go

@@ -38,7 +38,7 @@ type CursorConfig struct {
 	Throttler Throttler
 
 	ColumnsToSelect []string
-	BuildSelect     func([]string, *TableSchema, uint64, uint64) (squirrel.SelectBuilder, error)
+	BuildSelect     func([]string, *TableSchema, PaginationKey, uint64) (squirrel.SelectBuilder, error)
 	// BatchSize is a pointer to the BatchSize in Config.UpdatableConfig which can be independently updated from this code.
 	// Having it as a pointer allows the updated value to be read without needing additional code to copy the batch size value into the cursor config for each cursor we create.
 	BatchSize                 *uint64
@@ -47,7 +47,7 @@ type CursorConfig struct {
 }
 
 // returns a new Cursor with an embedded copy of itself
-func (c *CursorConfig) NewCursor(table *TableSchema, startPaginationKey, maxPaginationKey uint64) *Cursor {
+func (c *CursorConfig) NewCursor(table *TableSchema, startPaginationKey, maxPaginationKey PaginationKey) *Cursor {
 	return &Cursor{
 		CursorConfig:                *c,
 		Table:                       table,
@@ -58,7 +58,7 @@ func (c *CursorConfig) NewCursor(table *TableSchema, startPaginationKey, maxPagi
 }
 
 // returns a new Cursor with an embedded copy of itself
-func (c *CursorConfig) NewCursorWithoutRowLock(table *TableSchema, startPaginationKey, maxPaginationKey uint64) *Cursor {
+func (c *CursorConfig) NewCursorWithoutRowLock(table *TableSchema, startPaginationKey, maxPaginationKey PaginationKey) *Cursor {
 	cursor := c.NewCursor(table, startPaginationKey, maxPaginationKey)
 	cursor.RowLock = false
 	return cursor
@@ -77,11 +77,11 @@ type Cursor struct {
 	CursorConfig
 
 	Table            *TableSchema
-	MaxPaginationKey uint64
+	MaxPaginationKey PaginationKey
 	RowLock          bool
 
 	paginationKeyColumn         *schema.TableColumn
-	lastSuccessfulPaginationKey uint64
+	lastSuccessfulPaginationKey PaginationKey
 	logger                      *logrus.Entry
 }
 
@@ -96,10 +96,10 @@ func (c *Cursor) Each(f func(*RowBatch) error) error {
 		c.ColumnsToSelect = []string{"*"}
 	}
 
-	for c.lastSuccessfulPaginationKey < c.MaxPaginationKey {
+	for c.lastSuccessfulPaginationKey.Compare(c.MaxPaginationKey) < 0 {
 		var tx SqlPreparerAndRollbacker
 		var batch *RowBatch
-		var paginationKeypos uint64
+		var paginationKeypos PaginationKey
 
 		err := WithRetries(c.ReadRetries, 1*time.Second, c.logger, "fetch rows", func() (err error) {
 			if c.Throttler != nil {
@@ -137,9 +137,9 @@ func (c *Cursor) Each(f func(*RowBatch) error) error {
 			break
 		}
 
-		if paginationKeypos <= c.lastSuccessfulPaginationKey {
+		if paginationKeypos.Compare(c.lastSuccessfulPaginationKey) <= 0 {
 			tx.Rollback()
-			err = fmt.Errorf("new paginationKeypos %d <= lastSuccessfulPaginationKey %d", paginationKeypos, c.lastSuccessfulPaginationKey)
+			err = fmt.Errorf("new paginationKeypos %s <= lastSuccessfulPaginationKey %s", paginationKeypos.String(), c.lastSuccessfulPaginationKey.String())
 			c.logger.WithError(err).Errorf("last successful paginationKey position did not advance")
 			return err
 		}
@@ -159,7 +159,7 @@ func (c *Cursor) Each(f func(*RowBatch) error) error {
 	return nil
 }
 
-func (c *Cursor) Fetch(db SqlPreparer) (batch *RowBatch, paginationKeypos uint64, err error) {
+func (c *Cursor) Fetch(db SqlPreparer) (batch *RowBatch, paginationKeypos PaginationKey, err error) {
 	var selectBuilder squirrel.SelectBuilder
 	batchSize := c.CursorConfig.GetBatchSize(c.Table.Schema, c.Table.Name)
 
@@ -176,7 +176,7 @@ func (c *Cursor) Fetch(db SqlPreparer) (batch *RowBatch, paginationKeypos uint64
 	if c.RowLock {
 		mySqlVersion, err := c.DB.QueryMySQLVersion()
 		if err != nil {
-			return nil, 0, err
+			return nil, NewUint64Key(0), err
 		}
 		if strings.HasPrefix(mySqlVersion, "8.") {
 			selectBuilder = selectBuilder.Suffix("FOR SHARE NOWAIT")
@@ -261,9 +261,10 @@ func (c *Cursor) Fetch(db SqlPreparer) (batch *RowBatch, paginationKeypos uint64
 	}
 
 	if len(batchData) > 0 {
-		paginationKeypos, err = batchData[len(batchData)-1].GetUint64(paginationKeyIndex)
+		lastRowData := batchData[len(batchData)-1]
+		paginationKeypos, err = NewPaginationKeyFromRow(lastRowData, paginationKeyIndex, c.paginationKeyColumn)
 		if err != nil {
-			logger.WithError(err).Error("failed to get uint64 paginationKey value")
+			logger.WithError(err).Error("failed to get paginationKey value")
 			return
 		}
 	}
@@ -304,12 +305,12 @@ func ScanByteRow(rows *sqlorig.Rows, columnCount int) ([][]byte, error) {
 	return values, err
 }
 
-func DefaultBuildSelect(columns []string, table *TableSchema, lastPaginationKey, batchSize uint64) squirrel.SelectBuilder {
+func DefaultBuildSelect(columns []string, table *TableSchema, lastPaginationKey PaginationKey, batchSize uint64) squirrel.SelectBuilder {
 	quotedPaginationKey := QuoteField(table.GetPaginationColumn().Name)
 
 	return squirrel.Select(columns...).
 		From(QuotedTableName(table)).
-		Where(squirrel.Gt{quotedPaginationKey: lastPaginationKey}).
+		Where(squirrel.Gt{quotedPaginationKey: lastPaginationKey.SQLValue()}).
 		Limit(batchSize).
 		OrderBy(quotedPaginationKey)
 }