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returning.go
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returning.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.
package sql
import (
"bytes"
"golang.org/x/net/context"
"github.com/cockroachdb/cockroach/pkg/sql/parser"
"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
"github.com/cockroachdb/cockroach/pkg/util"
"github.com/pkg/errors"
)
// returningHelper implements the logic used for statements with RETURNING clauses. It accumulates
// result rows, one for each call to append().
type returningHelper struct {
p *planner
// Expected columns.
columns sqlbase.ResultColumns
// Processed copies of expressions from ReturningExprs.
exprs []parser.TypedExpr
rowCount int
source *dataSourceInfo
curSourceRow parser.Datums
// This struct must be allocated on the heap and its location stay
// stable after construction because it implements
// IndexedVarContainer and the IndexedVar objects in sub-expressions
// will link to it by reference after checkRenderStar / analyzeExpr.
// Enforce this using NoCopy.
noCopy util.NoCopy
}
// newReturningHelper creates a new returningHelper for use by an
// insert/update node.
func (p *planner) newReturningHelper(
ctx context.Context,
r parser.ReturningClause,
desiredTypes []parser.Type,
tn *parser.TableName,
tablecols []sqlbase.ColumnDescriptor,
) (*returningHelper, error) {
rh := &returningHelper{
p: p,
}
var rExprs parser.ReturningExprs
switch t := r.(type) {
case *parser.ReturningExprs:
rExprs = *t
case *parser.ReturningNothing, *parser.NoReturningClause:
return rh, nil
default:
panic(errors.Errorf("unexpected ReturningClause type: %T", t))
}
for _, e := range rExprs {
if err := p.parser.AssertNoAggregationOrWindowing(
e.Expr, "RETURNING", p.session.SearchPath,
); err != nil {
return nil, err
}
}
rh.columns = make(sqlbase.ResultColumns, 0, len(rExprs))
rh.source = newSourceInfoForSingleTable(
*tn, sqlbase.ResultColumnsFromColDescs(tablecols),
)
rh.exprs = make([]parser.TypedExpr, 0, len(rExprs))
ivarHelper := parser.MakeIndexedVarHelper(rh, len(tablecols))
for _, target := range rExprs {
cols, typedExprs, _, err := p.computeRenderAllowingStars(
ctx, target, parser.TypeAny, multiSourceInfo{rh.source}, ivarHelper,
autoGenerateRenderOutputName)
if err != nil {
return nil, err
}
rh.columns = append(rh.columns, cols...)
rh.exprs = append(rh.exprs, typedExprs...)
}
return rh, nil
}
// cookResultRow prepares a row according to the ReturningExprs, with input values
// from rowVals.
func (rh *returningHelper) cookResultRow(rowVals parser.Datums) (parser.Datums, error) {
if rh.exprs == nil {
rh.rowCount++
return rowVals, nil
}
rh.curSourceRow = rowVals
resRow := make(parser.Datums, len(rh.exprs))
for i, e := range rh.exprs {
d, err := e.Eval(&rh.p.evalCtx)
if err != nil {
return nil, err
}
resRow[i] = d
}
return resRow, nil
}
// IndexedVarEval implements the parser.IndexedVarContainer interface.
func (rh *returningHelper) IndexedVarEval(idx int, ctx *parser.EvalContext) (parser.Datum, error) {
return rh.curSourceRow[idx].Eval(ctx)
}
// IndexedVarResolvedType implements the parser.IndexedVarContainer interface.
func (rh *returningHelper) IndexedVarResolvedType(idx int) parser.Type {
return rh.source.sourceColumns[idx].Typ
}
// IndexedVarFormat implements the parser.IndexedVarContainer interface.
func (rh *returningHelper) IndexedVarFormat(buf *bytes.Buffer, f parser.FmtFlags, idx int) {
rh.source.FormatVar(buf, f, idx)
}