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expression.go
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expression.go
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// Copyright 2017 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: Radu Berinde (radu@cockroachlabs.com)
// This file contains helper code to populate distsqlrun.Expressions during
// planning.
package distsqlplan
import (
"bytes"
"fmt"
"golang.org/x/net/context"
"github.com/cockroachdb/cockroach/pkg/sql/distsqlrun"
"github.com/cockroachdb/cockroach/pkg/sql/parser"
"github.com/cockroachdb/cockroach/pkg/util/log"
)
// exprFmtFlagsBase are FmtFlags used for serializing expressions; a proper
// IndexedVar formatting function needs to be added on.
var exprFmtFlagsBase = parser.FmtStarDatumFormat(
parser.FmtParsable,
func(buf *bytes.Buffer, _ parser.FmtFlags) {
fmt.Fprintf(buf, "0")
},
)
// exprFmtFlagsNoMap are FmtFlags used for serializing expressions that don't
// need to remap IndexedVars.
var exprFmtFlagsNoMap = parser.FmtIndexedVarFormat(
exprFmtFlagsBase,
func(buf *bytes.Buffer, _ parser.FmtFlags, _ parser.IndexedVarContainer, idx int) {
fmt.Fprintf(buf, "@%d", idx+1)
},
)
// MakeExpression creates a distsqlrun.Expression.
//
// The distsqlrun.Expression uses the placeholder syntax (@1, @2, @3..) to refer
// to columns.
//
// The expr uses IndexedVars to refer to columns. The caller can optionally
// remap these columns by passing an indexVarMap: an IndexedVar with index i
// becomes column indexVarMap[i].
func MakeExpression(expr parser.TypedExpr, indexVarMap []int) distsqlrun.Expression {
if expr == nil {
return distsqlrun.Expression{}
}
// We format the expression using the IndexedVar and StarDatum formatting interceptors.
var f parser.FmtFlags
if indexVarMap == nil {
f = exprFmtFlagsNoMap
} else {
f = parser.FmtIndexedVarFormat(
exprFmtFlagsBase,
func(buf *bytes.Buffer, _ parser.FmtFlags, _ parser.IndexedVarContainer, idx int) {
remappedIdx := indexVarMap[idx]
if remappedIdx < 0 {
panic(fmt.Sprintf("unmapped index %d", idx))
}
fmt.Fprintf(buf, "@%d", remappedIdx+1)
},
)
}
var buf bytes.Buffer
expr.Format(&buf, f)
if log.V(1) {
log.Infof(context.TODO(), "Expr %s:\n%s", buf.String(), parser.ExprDebugString(expr))
}
return distsqlrun.Expression{Expr: buf.String()}
}