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plan: calc access path
when doing deriveStats
.
#6346
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Original file line number | Diff line number | Diff line change |
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@@ -14,13 +14,18 @@ | |
package plan | ||
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import ( | ||
"math" | ||
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"github.com/juju/errors" | ||
"github.com/pingcap/tidb/ast" | ||
"github.com/pingcap/tidb/expression" | ||
"github.com/pingcap/tidb/expression/aggregation" | ||
"github.com/pingcap/tidb/model" | ||
"github.com/pingcap/tidb/mysql" | ||
"github.com/pingcap/tidb/statistics" | ||
"github.com/pingcap/tidb/types" | ||
"github.com/pingcap/tidb/util/ranger" | ||
log "github.com/sirupsen/logrus" | ||
) | ||
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var ( | ||
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@@ -299,13 +304,85 @@ type DataSource struct { | |
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statisticTable *statistics.Table | ||
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// availableIndices is used for storing result of availableIndices function. | ||
availableIndices *availableIndices | ||
// possibleAccessPaths stores all the possible access path for physical plan, including table scan. | ||
possibleAccessPaths []*accessPath | ||
} | ||
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// accessPath tells how we access one index or just access table. | ||
type accessPath struct { | ||
index *model.IndexInfo | ||
ranges []*ranger.Range | ||
// countAfterAccess is the row count after we apply range seek and before we use other filter to filter data. | ||
countAfterAccess float64 | ||
// countAfterIndex is the row count after we apply filters on index and before we apply the table filters. | ||
countAfterIndex float64 | ||
accessConds []expression.Expression | ||
eqCondCount int | ||
indexFilters []expression.Expression | ||
tableFilters []expression.Expression | ||
// isTablePath indicates whether this path is table path. | ||
isTablePath bool | ||
// forced means this path is generated by `use/force index()`. | ||
forced bool | ||
} | ||
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func (ds *DataSource) deriveTablePathStats(path *accessPath) error { | ||
var err error | ||
sc := ds.ctx.GetSessionVars().StmtCtx | ||
path.countAfterAccess = float64(ds.statisticTable.Count) | ||
path.tableFilters = ds.pushedDownConds | ||
var pkCol *expression.Column | ||
if ds.tableInfo.PKIsHandle { | ||
if pkColInfo := ds.tableInfo.GetPkColInfo(); pkColInfo != nil { | ||
pkCol = expression.ColInfo2Col(ds.schema.Columns, pkColInfo) | ||
} | ||
} | ||
if pkCol == nil { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. We'better add some test cases to cover There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. We'better add some test cases to cover pkCol == nil and pkCol !=nil. There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. the status of pkCol is covered executor's unit test There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. But why all test cases can be passed when line 336~340 was missed before, There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. let me check it first. |
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path.ranges = ranger.FullIntRange(false) | ||
return nil | ||
} | ||
path.ranges = ranger.FullIntRange(mysql.HasUnsignedFlag(pkCol.RetType.Flag)) | ||
if len(ds.pushedDownConds) == 0 { | ||
return nil | ||
} | ||
path.accessConds, path.tableFilters = ranger.DetachCondsForTableRange(ds.ctx, ds.pushedDownConds, pkCol) | ||
path.ranges, err = ranger.BuildTableRange(path.accessConds, sc, pkCol.RetType) | ||
if err != nil { | ||
return errors.Trace(err) | ||
} | ||
path.countAfterAccess, err = ds.statisticTable.GetRowCountByIntColumnRanges(sc, pkCol.ID, path.ranges) | ||
return errors.Trace(err) | ||
} | ||
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type availableIndices struct { | ||
indices []*model.IndexInfo | ||
includeTableScan bool | ||
func (ds *DataSource) deriveIndexPathStats(path *accessPath) error { | ||
var err error | ||
sc := ds.ctx.GetSessionVars().StmtCtx | ||
path.ranges = ranger.FullRange() | ||
path.countAfterAccess = float64(ds.statisticTable.Count) | ||
idxCols, lengths := expression.IndexInfo2Cols(ds.schema.Columns, path.index) | ||
if len(idxCols) != 0 { | ||
path.ranges, path.accessConds, path.indexFilters, path.eqCondCount, err = ranger.DetachCondAndBuildRangeForIndex(ds.ctx, ds.pushedDownConds, idxCols, lengths) | ||
if err != nil { | ||
return errors.Trace(err) | ||
} | ||
path.countAfterAccess, err = ds.statisticTable.GetRowCountByIndexRanges(sc, path.index.ID, path.ranges) | ||
if err != nil { | ||
return errors.Trace(err) | ||
} | ||
path.indexFilters, path.tableFilters = splitIndexFilterConditions(path.indexFilters, path.index.Columns, ds.tableInfo) | ||
} else { | ||
path.indexFilters, path.tableFilters = splitIndexFilterConditions(ds.pushedDownConds, path.index.Columns, ds.tableInfo) | ||
} | ||
path.countAfterIndex = path.countAfterAccess | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Duplicated with line 364? There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. removed one. |
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if path.indexFilters != nil { | ||
selectivity, err := ds.statisticTable.Selectivity(ds.ctx, path.indexFilters) | ||
if err != nil { | ||
log.Warnf("An error happened: %v, we have to use the default selectivity", err.Error()) | ||
selectivity = selectionFactor | ||
} | ||
path.countAfterIndex = math.Max(path.countAfterAccess*selectivity, ds.statsAfterSelect.count) | ||
} | ||
return nil | ||
} | ||
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func (ds *DataSource) getPKIsHandleCol() *expression.Column { | ||
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This operation modifies
possibleAccessPaths
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We just iterate
possibleAccessPaths
and ignore table path at line 278.