vitess.io/vitess@v0.16.2/go/vt/binlog/keyspace_id_resolver.go (about)

     1  /*
     2  Copyright 2019 The Vitess Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package binlog
    18  
    19  import (
    20  	"fmt"
    21  	"strings"
    22  
    23  	"context"
    24  
    25  	"vitess.io/vitess/go/sqltypes"
    26  	"vitess.io/vitess/go/vt/key"
    27  	"vitess.io/vitess/go/vt/topo"
    28  	"vitess.io/vitess/go/vt/vtgate/vindexes"
    29  	"vitess.io/vitess/go/vt/vttablet/tabletserver/schema"
    30  )
    31  
    32  // keyspaceIDResolver is constructed for a tableMap entry in RBR.  It
    33  // is used for each row, and passed in the value used for figuring out
    34  // the keyspace id.
    35  type keyspaceIDResolver interface {
    36  	// keyspaceID takes a table row, and returns the keyspace id as bytes.
    37  	// It will return an error if no sharding key can be found.
    38  	// The bitmap describes which columns are present in the row.
    39  	keyspaceID(value sqltypes.Value) ([]byte, error)
    40  }
    41  
    42  // keyspaceIDResolverFactory creates a keyspaceIDResolver for a table
    43  // given its schema. It returns the index of the field to used to compute
    44  // the keyspaceID, and a function that given a value for that
    45  // field, returns the keyspace id.
    46  type keyspaceIDResolverFactory func(*schema.Table) (int, keyspaceIDResolver, error)
    47  
    48  // newKeyspaceIDResolverFactory creates a new
    49  // keyspaceIDResolverFactory for the provided keyspace and cell.
    50  func newKeyspaceIDResolverFactory(ctx context.Context, ts *topo.Server, keyspace string, cell string) (keyspaceIDResolverFactory, error) {
    51  	return newKeyspaceIDResolverFactoryV3(ctx, ts, keyspace, cell)
    52  }
    53  
    54  // newKeyspaceIDResolverFactoryV3 finds the SrvVSchema in the cell,
    55  // gets the keyspace part, and uses it to find the column name.
    56  func newKeyspaceIDResolverFactoryV3(ctx context.Context, ts *topo.Server, keyspace string, cell string) (keyspaceIDResolverFactory, error) {
    57  	srvVSchema, err := ts.GetSrvVSchema(ctx, cell)
    58  	if err != nil {
    59  		return nil, err
    60  	}
    61  	kschema, ok := srvVSchema.Keyspaces[keyspace]
    62  	if !ok {
    63  		return nil, fmt.Errorf("SrvVSchema has no entry for keyspace %v", keyspace)
    64  	}
    65  	keyspaceSchema, err := vindexes.BuildKeyspaceSchema(kschema, keyspace)
    66  	if err != nil {
    67  		return nil, fmt.Errorf("cannot build vschema for keyspace %v: %v", keyspace, err)
    68  	}
    69  	return func(table *schema.Table) (int, keyspaceIDResolver, error) {
    70  		// Find the v3 schema.
    71  		tableSchema, ok := keyspaceSchema.Tables[table.Name.String()]
    72  		if !ok {
    73  			return -1, nil, fmt.Errorf("no vschema definition for table %v", table.Name)
    74  		}
    75  
    76  		// use the lowest cost unique vindex as the sharding key
    77  		colVindex, err := vindexes.FindVindexForSharding(table.Name.String(), tableSchema.ColumnVindexes)
    78  		if err != nil {
    79  			return -1, nil, err
    80  		}
    81  
    82  		// TODO @rafael - when rewriting the mapping function, this will need to change.
    83  		// for now it's safe to assume the sharding key will be always on index 0.
    84  		shardingColumnName := colVindex.Columns[0].String()
    85  		for i, col := range table.Fields {
    86  			if strings.EqualFold(col.Name, shardingColumnName) {
    87  				// We found the column.
    88  				return i, &keyspaceIDResolverFactoryV3{
    89  					// Only SingleColumn vindexes are returned by FindVindexForSharding.
    90  					vindex: colVindex.Vindex.(vindexes.SingleColumn),
    91  				}, nil
    92  			}
    93  		}
    94  		// The column was not found.
    95  		return -1, nil, fmt.Errorf("cannot find column %v in table %v", shardingColumnName, table.Name)
    96  	}, nil
    97  }
    98  
    99  // keyspaceIDResolverFactoryV3 uses the Vindex to compute the value.
   100  type keyspaceIDResolverFactoryV3 struct {
   101  	vindex vindexes.SingleColumn
   102  }
   103  
   104  func (r *keyspaceIDResolverFactoryV3) keyspaceID(v sqltypes.Value) ([]byte, error) {
   105  	destinations, err := r.vindex.Map(context.TODO(), nil, []sqltypes.Value{v})
   106  	if err != nil {
   107  		return nil, err
   108  	}
   109  	if len(destinations) != 1 {
   110  		return nil, fmt.Errorf("mapping row to keyspace id returned an invalid array of destinations: %v", key.DestinationsString(destinations))
   111  	}
   112  	ksid, ok := destinations[0].(key.DestinationKeyspaceID)
   113  	if !ok || len(ksid) == 0 {
   114  		return nil, fmt.Errorf("could not map %v to a keyspace id, got destination %v", v, destinations[0])
   115  	}
   116  	return ksid, nil
   117  }