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needed_columns.go
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needed_columns.go
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// Copyright 2016 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
//
// Author: Raphael 'kena' Poss (knz@cockroachlabs.com)
package sql
import (
"fmt"
"github.com/cockroachdb/cockroach/pkg/sql/parser"
"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
)
// setNeededColumns informs the node about which columns are
// effectively needed by the consumer of its result rows.
func setNeededColumns(plan planNode, needed []bool) {
switch n := plan.(type) {
case *createTableNode:
if n.n.As() {
setNeededColumns(n.sourcePlan, allColumns(n.sourcePlan))
}
case *createViewNode:
setNeededColumns(n.sourcePlan, allColumns(n.sourcePlan))
case *explainDebugNode:
setNeededColumns(n.plan, allColumns(n.plan))
case *explainDistSQLNode:
setNeededColumns(n.plan, allColumns(n.plan))
case *explainTraceNode:
setNeededColumns(n.plan, allColumns(n.plan))
case *explainPlanNode:
if n.optimized {
setNeededColumns(n.plan, allColumns(n.plan))
}
case *limitNode:
setNeededColumns(n.plan, needed)
case *indexJoinNode:
// Currently all the needed result columns are provided by the
// table sub-source; from the index sub-source we only need the PK
// columns sufficient to configure the table sub-source.
// TODO(radu/knz): see the comments at the start of index_join.go,
// perhaps this can be optimized to utilize the column values
// already provided by the index instead of re-retrieving them
// using the table scanNode.
setNeededColumns(n.table, needed)
setNeededColumns(n.index, n.primaryKeyColumns)
case *unionNode:
if !n.emitAll {
// For UNION (as opposed to UNION ALL) we have to check for
// uniqueness so we need all the columns.
needed = allColumns(n)
}
setNeededColumns(n.left, needed)
setNeededColumns(n.right, needed)
case *joinNode:
// Note: getNeededColumns takes into account both the columns
// tested for equality and the join predicate expression.
leftNeeded, rightNeeded := n.pred.getNeededColumns(needed)
setNeededColumns(n.left.plan, leftNeeded)
setNeededColumns(n.right.plan, rightNeeded)
markOmitted(n.columns, needed)
case *ordinalityNode:
setNeededColumns(n.source, needed[:len(needed)-1])
markOmitted(n.columns[:len(needed)-1], needed[:len(needed)-1])
case *valuesNode:
markOmitted(n.columns, needed)
case *scanNode:
copy(n.valNeededForCol, needed)
for i := range needed {
// All the values involved in the filter expression are needed too.
if n.filterVars.IndexedVarUsed(i) {
n.valNeededForCol[i] = true
}
}
markOmitted(n.resultColumns, n.valNeededForCol)
case *distinctNode:
// Distinct needs values for every input column.
setNeededColumns(n.plan, allColumns(n.plan))
case *filterNode:
// Detect which columns from the source are needed in addition to
// those needed by the context.
sourceNeeded := make([]bool, len(n.source.info.sourceColumns))
copy(sourceNeeded, needed)
for i := range sourceNeeded {
sourceNeeded[i] = sourceNeeded[i] || n.ivarHelper.IndexedVarUsed(i)
}
setNeededColumns(n.source.plan, sourceNeeded)
case *renderNode:
// Optimization: remove all the render expressions that are not
// needed. While doing so, some indexed vars may disappear
// entirely, which may enable omission of more columns from the
// source. To detect this, we need to reset the IndexedVarHelper
// and re-bind all the expressions.
n.ivarHelper.Reset()
for i, val := range needed {
if !val {
// This render is not used, so reduce its expression to NULL.
n.render[i] = parser.DNull
continue
}
n.render[i] = n.ivarHelper.Rebind(n.render[i], false, true)
}
// Now detect which columns from the source are still needed.
sourceNeeded := make([]bool, len(n.source.info.sourceColumns))
for i := range sourceNeeded {
sourceNeeded[i] = n.ivarHelper.IndexedVarUsed(i)
}
setNeededColumns(n.source.plan, sourceNeeded)
markOmitted(n.columns, needed)
case *sortNode:
sourceNeeded := make([]bool, len(n.plan.Columns()))
copy(sourceNeeded[:len(needed)], needed)
// All the ordering columns are also needed.
for _, o := range n.ordering {
sourceNeeded[o.ColIdx] = true
}
setNeededColumns(n.plan, sourceNeeded)
markOmitted(n.columns, sourceNeeded[:len(n.columns)])
case *groupNode:
// TODO(knz): This can be optimized by removing the aggregation
// results that are not needed, then removing additional renders
// from the source that would otherwise only be needed for the
// omitted aggregation results.
setNeededColumns(n.plan, allColumns(n.plan))
case *windowNode:
// TODO(knz): This can be optimized by removing the window function
// definitions that are not needed, then removing additional
// renders from the source that would otherwise only be needed for
// the omitted window definitions.
setNeededColumns(n.plan, allColumns(n.plan))
case *deleteNode:
// TODO(knz): This can be optimized by omitting the columns that
// are not part of the primary key, do not participate in
// foreign key relations and that are not needed for RETURNING.
setNeededColumns(n.run.rows, allColumns(n.run.rows))
case *updateNode:
// TODO(knz): This can be optimized by omitting the columns that
// are not part of the primary key, do not participate in
// foreign key relations and that are not needed for RETURNING.
setNeededColumns(n.run.rows, allColumns(n.run.rows))
case *insertNode:
// TODO(knz): This can be optimized by omitting the columns that
// are not part of the primary key, do not participate in
// foreign key relations and that are not needed for RETURNING.
setNeededColumns(n.run.rows, allColumns(n.run.rows))
case *splitNode:
setNeededColumns(n.rows, allColumns(n.rows))
case *relocateNode:
setNeededColumns(n.rows, allColumns(n.rows))
case *alterTableNode:
case *copyNode:
case *createDatabaseNode:
case *createIndexNode:
case *createUserNode:
case *delayedNode:
case *dropDatabaseNode:
case *dropIndexNode:
case *dropTableNode:
case *dropViewNode:
case *emptyNode:
case *hookFnNode:
case *valueGenerator:
case *showRangesNode:
case *scatterNode:
default:
panic(fmt.Sprintf("unhandled node type: %T", plan))
}
}
// allColumns returns true for every column produced by the plan.
func allColumns(plan planNode) []bool {
needed := make([]bool, len(plan.Columns()))
for i := range needed {
needed[i] = true
}
return needed
}
// markOmitted propagates the information from the needed array back
// to the sqlbase.ResultColumns array.
func markOmitted(cols sqlbase.ResultColumns, needed []bool) {
for i, val := range needed {
cols[i].Omitted = !val
}
}