github.com/hasnat/dolt/go@v0.0.0-20210628190320-9eb5d843fbb7/libraries/doltcore/table/table_reader.go (about)

     1  // Copyright 2020 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package table
    16  
    17  import (
    18  	"context"
    19  	"fmt"
    20  
    21  	"github.com/dolthub/go-mysql-server/sql"
    22  
    23  	"github.com/dolthub/dolt/go/libraries/doltcore/doltdb"
    24  	"github.com/dolthub/dolt/go/libraries/doltcore/row"
    25  	"github.com/dolthub/dolt/go/libraries/doltcore/schema"
    26  	"github.com/dolthub/dolt/go/store/types"
    27  )
    28  
    29  // TableReader is an interface for reading rows from a table
    30  type TableReader interface {
    31  	// GetSchema gets the schema of the rows that this reader will return
    32  	GetSchema() schema.Schema
    33  
    34  	// ReadRow reads a row from a table.  If there is a bad row the returned error will be non nil, and calling
    35  	// IsBadRow(err) will be return true. This is a potentially non-fatal error and callers can decide if they want to
    36  	// continue on a bad row, or fail.
    37  	ReadRow(ctx context.Context) (row.Row, error)
    38  }
    39  
    40  // TableCloser is an interface for a table stream that can be closed to release resources
    41  type TableCloser interface {
    42  	// Close should release resources being held
    43  	Close(ctx context.Context) error
    44  }
    45  
    46  // TableReadCloser is an interface for reading rows from a table, that can be closed.
    47  type TableReadCloser interface {
    48  	TableReader
    49  	TableCloser
    50  }
    51  
    52  // SqlTableReader is a  TableReader that can read rows as sql.Row.
    53  type SqlTableReader interface {
    54  	// GetSchema gets the schema of the rows that this reader will return
    55  	GetSchema() schema.Schema
    56  
    57  	// ReadRow reads a row from a table as go-mysql-server sql.Row.
    58  	ReadSqlRow(ctx context.Context) (sql.Row, error)
    59  }
    60  
    61  // NewTableReader creates a SqlTableReader from |tbl| starting from the first record.
    62  func NewTableReader(ctx context.Context, tbl *doltdb.Table) (SqlTableReader, error) {
    63  	sch, err := tbl.GetSchema(ctx)
    64  	if err != nil {
    65  		return nil, err
    66  	}
    67  
    68  	if schema.IsKeyless(sch) {
    69  		return newKeylessTableReader(ctx, tbl, sch, false)
    70  	}
    71  	return newPkTableReader(ctx, tbl, sch, false)
    72  }
    73  
    74  // NewDoltTableReader creates a SqlTableReader from |tbl| starting from the first record.
    75  func NewDoltTableReader(ctx context.Context, tbl *doltdb.Table) (TableReadCloser, error) {
    76  	sch, err := tbl.GetSchema(ctx)
    77  	if err != nil {
    78  		return nil, err
    79  	}
    80  
    81  	if schema.IsKeyless(sch) {
    82  		return newKeylessTableReader(ctx, tbl, sch, false)
    83  	}
    84  	return newPkTableReader(ctx, tbl, sch, false)
    85  }
    86  
    87  // NewBufferedTableReader creates a buffered SqlTableReader from |tbl| starting from the first record.
    88  func NewBufferedTableReader(ctx context.Context, tbl *doltdb.Table) (SqlTableReader, error) {
    89  	sch, err := tbl.GetSchema(ctx)
    90  	if err != nil {
    91  		return nil, err
    92  	}
    93  
    94  	if schema.IsKeyless(sch) {
    95  		return newKeylessTableReader(ctx, tbl, sch, true)
    96  	}
    97  	return newPkTableReader(ctx, tbl, sch, true)
    98  }
    99  
   100  // NewBufferedTableReader creates a buffered SqlTableReader from |tbl| starting from the first record.
   101  func NewBufferedReaderForRows(ctx context.Context, rowData types.Map, sch schema.Schema) (SqlTableReader, error) {
   102  	if schema.IsKeyless(sch) {
   103  		return newKeylessTableReaderForRows(ctx, rowData, sch, true)
   104  	}
   105  	return newPkTableReaderForRows(ctx, rowData, sch, true)
   106  }
   107  
   108  // NewBufferedTableReaderForPartition creates a SqlTableReader that reads the rows of |tbl| with indexes
   109  // in the half-open interval [start, end).
   110  func NewBufferedTableReaderForPartition(ctx context.Context, tbl *doltdb.Table, start, end uint64) (SqlTableReader, error) {
   111  	if start > end {
   112  		return nil, fmt.Errorf("invalid partition table reader, start (%d) > end (%d)", start, end)
   113  	}
   114  
   115  	sch, err := tbl.GetSchema(ctx)
   116  	if err != nil {
   117  		return nil, err
   118  	}
   119  
   120  	if schema.IsKeyless(sch) {
   121  		return newKeylessTableReaderForPartition(ctx, tbl, sch, start, end)
   122  	}
   123  	return newPkTableReaderForPartition(ctx, tbl, sch, start, end)
   124  }
   125  
   126  // NewTableReaderFrom creates a SqlTableReader that reads the rows of |tbl| beginning at the record
   127  // whose types.Map key is >= |val|.
   128  func NewTableReaderFrom(ctx context.Context, tbl *doltdb.Table, val types.Value) (SqlTableReader, error) {
   129  	sch, err := tbl.GetSchema(ctx)
   130  	if err != nil {
   131  		return nil, err
   132  	}
   133  
   134  	if schema.IsKeyless(sch) {
   135  		return newKeylessTableReaderFrom(ctx, tbl, sch, val)
   136  	}
   137  	return newPkTableReaderFrom(ctx, tbl, sch, val)
   138  }