github.com/whtcorpsinc/MilevaDB-Prod@v0.0.0-20211104133533-f57f4be3b597/interlock/explain.go (about)

     1  // Copyright 2020 WHTCORPS INC, 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  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package interlock
    15  
    16  import (
    17  	"context"
    18  
    19  	"github.com/cznic/mathutil"
    20  	"github.com/whtcorpsinc/errors"
    21  	"github.com/whtcorpsinc/milevadb/causet/embedded"
    22  	"github.com/whtcorpsinc/milevadb/soliton/chunk"
    23  )
    24  
    25  // ExplainInterDirc represents an explain interlock.
    26  type ExplainInterDirc struct {
    27  	baseInterlockingDirectorate
    28  
    29  	explain          *embedded.Explain
    30  	analyzeInterDirc InterlockingDirectorate
    31  	rows             [][]string
    32  	cursor           int
    33  }
    34  
    35  // Open implements the InterlockingDirectorate Open interface.
    36  func (e *ExplainInterDirc) Open(ctx context.Context) error {
    37  	if e.analyzeInterDirc != nil {
    38  		return e.analyzeInterDirc.Open(ctx)
    39  	}
    40  	return nil
    41  }
    42  
    43  // Close implements the InterlockingDirectorate Close interface.
    44  func (e *ExplainInterDirc) Close() error {
    45  	e.rows = nil
    46  	return nil
    47  }
    48  
    49  // Next implements the InterlockingDirectorate Next interface.
    50  func (e *ExplainInterDirc) Next(ctx context.Context, req *chunk.Chunk) error {
    51  	if e.rows == nil {
    52  		var err error
    53  		e.rows, err = e.generateExplainInfo(ctx)
    54  		if err != nil {
    55  			return err
    56  		}
    57  	}
    58  
    59  	req.GrowAndReset(e.maxChunkSize)
    60  	if e.cursor >= len(e.rows) {
    61  		return nil
    62  	}
    63  
    64  	numCurEvents := mathutil.Min(req.Capacity(), len(e.rows)-e.cursor)
    65  	for i := e.cursor; i < e.cursor+numCurEvents; i++ {
    66  		for j := range e.rows[i] {
    67  			req.AppendString(j, e.rows[i][j])
    68  		}
    69  	}
    70  	e.cursor += numCurEvents
    71  	return nil
    72  }
    73  
    74  func (e *ExplainInterDirc) generateExplainInfo(ctx context.Context) (rows [][]string, err error) {
    75  	closed := false
    76  	defer func() {
    77  		if !closed && e.analyzeInterDirc != nil {
    78  			err = e.analyzeInterDirc.Close()
    79  			closed = true
    80  		}
    81  	}()
    82  	if e.analyzeInterDirc != nil {
    83  		chk := newFirstChunk(e.analyzeInterDirc)
    84  		var nextErr, closeErr error
    85  		for {
    86  			nextErr = Next(ctx, e.analyzeInterDirc, chk)
    87  			if nextErr != nil || chk.NumEvents() == 0 {
    88  				break
    89  			}
    90  		}
    91  		closeErr = e.analyzeInterDirc.Close()
    92  		closed = true
    93  		if nextErr != nil {
    94  			if closeErr != nil {
    95  				err = errors.New(nextErr.Error() + ", " + closeErr.Error())
    96  			} else {
    97  				err = nextErr
    98  			}
    99  		} else if closeErr != nil {
   100  			err = closeErr
   101  		}
   102  		if err != nil {
   103  			return nil, err
   104  		}
   105  	}
   106  	if err = e.explain.RenderResult(); err != nil {
   107  		return nil, err
   108  	}
   109  	if e.analyzeInterDirc != nil {
   110  		e.ctx.GetStochastikVars().StmtCtx.RuntimeStatsDefCausl = nil
   111  	}
   112  	return e.explain.Events, nil
   113  }