MySQL sharding storage

pkg/providers/mysql/storage_sharding.go

@@ -0,0 +1,53 @@
+package mysql
+
+import (
+	"context"
+	"fmt"
+	"github.com/doublecloud/transfer/internal/logger"
+	"github.com/doublecloud/transfer/library/go/core/xerrors"
+	"github.com/doublecloud/transfer/pkg/abstract"
+)
+
+func (s *Storage) ShardTable(ctx context.Context, table abstract.TableDescription) ([]abstract.TableDescription, error) {
+	partitions, err := s.resolvePartitions(ctx, table)
+	if err != nil {
+		logger.Log.Warnf("unable to load child tables: %v", err)
+	}
+	if len(partitions) > 0 {
+		return partitions, nil
+	}
+
+	return []abstract.TableDescription{table}, nil
+}
+
+func (s *Storage) resolvePartitions(ctx context.Context, table abstract.TableDescription) ([]abstract.TableDescription, error) {
+	rows, err := s.DB.QueryContext(
+		ctx,
+		`
+SELECT PARTITION_NAME, TABLE_ROWS
+FROM INFORMATION_SCHEMA.PARTITIONS
+WHERE TABLE_SCHEMA = ? AND TABLE_NAME = ?;
+`,
+		table.Schema,
+		table.Name,
+	)
+	if err != nil {
+		return nil, xerrors.Errorf("unable to resolve partitions: %w", err)
+	}
+	var res []abstract.TableDescription
+	for rows.Next() {
+		var partName string
+		var tableRows int
+		if err := rows.Scan(&partName, &tableRows); err != nil {
+			return nil, xerrors.Errorf("unable to scan partition: %w", err)
+		}
+		res = append(res, abstract.TableDescription{
+			Name:   table.Name,
+			Schema: table.Schema,
+			Filter: abstract.WhereStatement(fmt.Sprintf("PARTITION (%s)", partName)),
+			EtaRow: uint64(tableRows),
+			Offset: 0,
+		})
+	}
+	return res, nil
+}

pkg/providers/mysql/tests/sharding/dump/source.sql

@@ -0,0 +1,21 @@
+CREATE TABLE orders (
+    id INT NOT NULL AUTO_INCREMENT,
+    order_date DATE NOT NULL,
+    customer_name VARCHAR(100),
+    amount DECIMAL(10,2),
+    PRIMARY KEY (id, order_date)
+)
+PARTITION BY RANGE (YEAR(order_date)) (
+    PARTITION p2022 VALUES LESS THAN (2023),
+    PARTITION p2023 VALUES LESS THAN (2024),
+    PARTITION p2024 VALUES LESS THAN (2025),
+    PARTITION p_future VALUES LESS THAN MAXVALUE
+);
+
+INSERT INTO orders (order_date, customer_name, amount) VALUES
+   ('2022-05-10', 'Alice', 150.00),
+   ('2022-08-21', 'Bob', 200.00),
+   ('2023-03-15', 'Charlie', 300.00),
+   ('2023-11-05', 'David', 400.00),
+   ('2024-01-10', 'Eve', 500.00),
+   ('2024-07-18', 'Frank', 600.00);

pkg/providers/mysql/tests/sharding/storage_sharding_test.go

@@ -0,0 +1,40 @@
+package sharding
+
+import (
+	"context"
+	"github.com/doublecloud/transfer/pkg/abstract"
+	"github.com/doublecloud/transfer/pkg/providers/mysql"
+	"github.com/doublecloud/transfer/pkg/providers/mysql/mysqlrecipe"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestShardingByPartitions(t *testing.T) {
+	source := mysqlrecipe.RecipeMysqlSource()
+	storage, err := mysql.NewStorage(source.ToStorageParams())
+	require.NoError(t, err)
+	parts, err := storage.ShardTable(context.Background(), abstract.TableDescription{
+		Name:   "orders",
+		Schema: source.Database,
+		Filter: "",
+		EtaRow: 0,
+		Offset: 0,
+	})
+	require.NoError(t, err)
+	require.Len(t, parts, 4)
+	resRows := 0
+	for _, part := range parts {
+		require.NoError(
+			t,
+			storage.LoadTable(context.Background(), part, func(items []abstract.ChangeItem) error {
+				for _, r := range items {
+					if r.IsRowEvent() {
+						resRows++
+					}
+				}
+				return nil
+			}),
+		)
+	}
+	require.Equal(t, resRows, 6)
+}

pkg/providers/mysql/utils.go

@@ -118,7 +118,11 @@ func buildSelectQuery(table abstract.TableDescription, tableSchema []abstract.Co
 	)
 
 	if table.Filter != "" {
-		resultQuery += " WHERE " + string(table.Filter)
+		if IsPartition(table.Filter) {
+			resultQuery += string(table.Filter)
+		} else {
+			resultQuery += " WHERE " + string(table.Filter)
+		}
 	}
 	if table.Offset != 0 {
 		resultQuery += fmt.Sprintf(" OFFSET %d", table.Offset)
@@ -127,6 +131,10 @@ func buildSelectQuery(table abstract.TableDescription, tableSchema []abstract.Co
 	return resultQuery
 }
 
+func IsPartition(filter abstract.WhereStatement) bool {
+	return strings.HasPrefix(string(filter), "PARTITION")
+}
+
 func MakeArrBacktickedColumnNames(tableSchema *[]abstract.ColSchema) []string {
 	colNames := make([]string, len(*tableSchema))
 	for idx, col := range *tableSchema {