github.com/dolthub/dolt/go@v0.40.5-0.20240520175717-68db7794bea6/libraries/doltcore/table/table_iterator.go (about)

     1  // Copyright 2022 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  
    20  	"github.com/dolthub/go-mysql-server/sql"
    21  
    22  	"github.com/dolthub/dolt/go/libraries/doltcore/doltdb/durable"
    23  	"github.com/dolthub/dolt/go/libraries/doltcore/schema"
    24  	"github.com/dolthub/dolt/go/libraries/doltcore/sqle/index"
    25  	"github.com/dolthub/dolt/go/store/types"
    26  )
    27  
    28  // RowIter wraps a sql.RowIter and abstracts away sql.Context for a
    29  // context.Context.
    30  type RowIter interface {
    31  	Next(ctx context.Context) (sql.Row, error)
    32  	Close(ctx context.Context) error
    33  }
    34  
    35  type rowIterImpl struct {
    36  	inner  sql.RowIter
    37  	sqlCtx *sql.Context
    38  }
    39  
    40  // NewRowIter returns a RowIter that wraps |inner|. Ctx passed to Next is
    41  // converted to *sql.Context.
    42  func NewRowIter(inner sql.RowIter) RowIter {
    43  	return rowIterImpl{inner: inner}
    44  }
    45  
    46  // Next implements RowIter.
    47  func (i rowIterImpl) Next(ctx context.Context) (sql.Row, error) {
    48  	r, err := i.inner.Next(&sql.Context{Context: ctx})
    49  	if err != nil {
    50  		return nil, err
    51  	}
    52  	return r, nil
    53  }
    54  
    55  // Close implements RowIter.
    56  func (i rowIterImpl) Close(ctx context.Context) error {
    57  	return i.inner.Close(&sql.Context{Context: ctx})
    58  }
    59  
    60  // NewTableIterator creates a RowIter that iterates sql.Row's from |idx|.
    61  // |offset| can be supplied to read at some start point in |idx|.
    62  func NewTableIterator(ctx context.Context, sch schema.Schema, idx durable.Index, offset uint64) (RowIter, error) {
    63  	var rowItr sql.RowIter
    64  	if types.IsFormat_DOLT(idx.Format()) {
    65  		m := durable.ProllyMapFromIndex(idx)
    66  		c, err := m.Count()
    67  		if err != nil {
    68  			return nil, err
    69  		}
    70  		itr, err := m.IterOrdinalRange(ctx, offset, uint64(c))
    71  		if err != nil {
    72  			return nil, err
    73  		}
    74  		rowItr = index.NewProllyRowIterForMap(sch, m, itr, nil)
    75  		if err != nil {
    76  			return nil, err
    77  		}
    78  	} else {
    79  
    80  		noms := durable.NomsMapFromIndex(idx)
    81  		itr, err := noms.IteratorAt(ctx, offset)
    82  		if err != nil {
    83  			return nil, err
    84  		}
    85  		conv := makeNomsConverter(idx.Format(), sch)
    86  		rowItr = index.NewDoltMapIter(itr.NextTuple, nil, conv)
    87  	}
    88  	return NewRowIter(rowItr), nil
    89  }
    90  
    91  // makeNomsConverter creates a *index.KVToSqlRowConverter.
    92  func makeNomsConverter(nbf *types.NomsBinFormat, sch schema.Schema) *index.KVToSqlRowConverter {
    93  	cols := sch.GetAllCols().GetColumns()
    94  	tagToSqlColIdx := make(map[uint64]int)
    95  	for i, col := range cols {
    96  		tagToSqlColIdx[col.Tag] = i
    97  	}
    98  	return index.NewKVToSqlRowConverter(nbf, tagToSqlColIdx, cols, len(cols))
    99  }