Golang TableDescriptor.FindColumnByID方法代码示例

func makeIndexKeyVals(desc *structured.TableDescriptor,
	index structured.IndexDescriptor) ([]parser.Datum, error) {
	vals := make([]parser.Datum, len(index.ColumnIDs))
	for i, id := range index.ColumnIDs {
		col, err := desc.FindColumnByID(id)
		if err != nil {
			return nil, err
		}
		switch col.Type.Kind {
		case structured.ColumnType_BIT, structured.ColumnType_INT:
			vals[i] = parser.DInt(0)
		case structured.ColumnType_FLOAT:
			vals[i] = parser.DFloat(0)
		case structured.ColumnType_CHAR, structured.ColumnType_TEXT,
			structured.ColumnType_BLOB:
			vals[i] = parser.DString("")
		default:
			return nil, util.Errorf("TODO(pmattis): decoded index key: %s", col.Type.Kind)
		}
	}
	if !index.Unique {
		// Non-unique columns are suffixed by the primary index key.
		pkVals, err := makeIndexKeyVals(desc, desc.PrimaryIndex)
		if err != nil {
			return nil, err
		}
		vals = append(vals, pkVals...)
	}
	return vals, nil
}

func decodeIndexKey(desc *structured.TableDescriptor,
	index structured.IndexDescriptor, vals map[string]parser.Datum, key []byte) ([]byte, error) {
	if !bytes.HasPrefix(key, keys.TableDataPrefix) {
		return nil, fmt.Errorf("%s: invalid key prefix: %q", desc.Name, key)
	}
	key = bytes.TrimPrefix(key, keys.TableDataPrefix)

	var tableID uint64
	key, tableID = encoding.DecodeUvarint(key)
	if uint32(tableID) != desc.ID {
		return nil, fmt.Errorf("%s: unexpected table ID: %d != %d", desc.Name, desc.ID, tableID)
	}

	var indexID uint64
	key, indexID = encoding.DecodeUvarint(key)
	if uint32(indexID) != index.ID {
		return nil, fmt.Errorf("%s: unexpected index ID: %d != %d", desc.Name, index.ID, indexID)
	}

	for _, id := range index.ColumnIDs {
		col, err := desc.FindColumnByID(id)
		if err != nil {
			return nil, err
		}
		switch col.Type.Kind {
		case structured.ColumnType_BIT, structured.ColumnType_INT:
			var i int64
			key, i = encoding.DecodeVarint(key)
			vals[col.Name] = parser.DInt(i)
		case structured.ColumnType_FLOAT:
			var f float64
			key, f = encoding.DecodeNumericFloat(key)
			vals[col.Name] = parser.DFloat(f)
		case structured.ColumnType_CHAR, structured.ColumnType_TEXT,
			structured.ColumnType_BLOB:
			var r []byte
			key, r = encoding.DecodeBytes(key, nil)
			vals[col.Name] = parser.DString(r)
		default:
			return nil, util.Errorf("TODO(pmattis): decoded index key: %s", col.Type.Kind)
		}
	}

	return key, nil
}

// Select selects rows from a single table.
func (s *Server) Select(session *Session, p *parser.Select, args []sqlwire.Datum, resp *sqlwire.Response) error {
	if len(p.Exprs) != 1 {
		return fmt.Errorf("TODO(pmattis): unsupported select exprs: %s", p.Exprs)
	}
	if _, ok := p.Exprs[0].(*parser.StarExpr); !ok {
		return fmt.Errorf("TODO(pmattis): unsupported select expr: %s", p.Exprs)
	}

	if len(p.From) != 1 {
		return fmt.Errorf("TODO(pmattis): unsupported from: %s", p.From)
	}
	var desc *structured.TableDescriptor
	{
		ate, ok := p.From[0].(*parser.AliasedTableExpr)
		if !ok {
			return fmt.Errorf("TODO(pmattis): unsupported from: %s", p.From)
		}
		table, ok := ate.Expr.(parser.QualifiedName)
		if !ok {
			return fmt.Errorf("TODO(pmattis): unsupported from: %s", p.From)
		}
		var err error
		desc, err = s.getTableDesc(session.Database, table)
		if err != nil {
			return err
		}
	}

	// Retrieve all of the keys that start with our index key prefix.
	startKey := proto.Key(encodeIndexKeyPrefix(desc.ID, desc.Indexes[0].ID))
	endKey := startKey.PrefixEnd()
	sr, err := s.db.Scan(startKey, endKey, 0)
	if err != nil {
		return err
	}

	// All of the columns for a particular row will be grouped together. We loop
	// over the returned key/value pairs and decode the key to extract the
	// columns encoded within the key and the column ID. We use the column ID to
	// lookup the column and decode the value. All of these values go into a map
	// keyed by column name. When the index key changes we output a row
	// containing the current values.
	//
	// The TODOs here are too numerous to list. This is only performing a full
	// table scan using the primary key.

	var rows []sqlwire.Result_Row
	var primaryKey []byte
	vals := valMap{}
	for _, kv := range sr {
		if primaryKey != nil && !bytes.HasPrefix(kv.Key, primaryKey) {
			if output, err := shouldOutputRow(p.Where, vals); err != nil {
				return err
			} else if output {
				rows = append(rows, outputRow(desc.Columns, vals))
			}
			vals = valMap{}
		}

		remaining, err := decodeIndexKey(desc, desc.Indexes[0], vals, kv.Key)
		if err != nil {
			return err
		}
		primaryKey = []byte(kv.Key[:len(kv.Key)-len(remaining)])

		_, colID := encoding.DecodeUvarint(remaining)
		if err != nil {
			return err
		}
		col, err := desc.FindColumnByID(uint32(colID))
		if err != nil {
			return err
		}
		vals[col.Name] = unmarshalValue(*col, kv)

		if log.V(2) {
			log.Infof("Scan %q -> %v", kv.Key, vals[col.Name])
		}
	}

	if output, err := shouldOutputRow(p.Where, vals); err != nil {
		return err
	} else if output {
		rows = append(rows, outputRow(desc.Columns, vals))
	}

	resp.Results = []sqlwire.Result{
		{
			Columns: make([]string, len(desc.Columns)),
			Rows:    rows,
		},
	}
	for i, col := range desc.Columns {
		resp.Results[0].Columns[i] = col.Name
	}
	return nil
}