forked from cockroachdb/cockroach
/
expr.go
140 lines (119 loc) · 3.9 KB
/
expr.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: Radu Berinde (radu@cockroachlabs.com)
package distsql
import (
"fmt"
"strconv"
"github.com/cockroachdb/cockroach/sql/parser"
"github.com/cockroachdb/cockroach/sql/sqlbase"
"github.com/pkg/errors"
)
// valArgsConvert is a parser.Visitor that converts Placeholders ($0, $1, etc.) to
// IndexedVars.
type valArgsConvert struct {
h *parser.IndexedVarHelper
err error
}
func (v *valArgsConvert) VisitPre(expr parser.Expr) (recurse bool, newExpr parser.Expr) {
if val, ok := expr.(parser.Placeholder); ok {
idx, err := strconv.Atoi(val.Name)
if err != nil || idx < 0 || idx >= v.h.NumVars() {
v.err = errors.Errorf("invalid variable index %s", val.Name)
return false, expr
}
return false, v.h.IndexedVar(idx)
}
return true, expr
}
func (*valArgsConvert) VisitPost(expr parser.Expr) parser.Expr { return expr }
// processExpression parses the string expression inside an Expression,
// interpreting $0, $1, etc as indexed variables.
func processExpression(exprSpec Expression, h *parser.IndexedVarHelper) (parser.TypedExpr, error) {
if exprSpec.Expr == "" {
return nil, nil
}
expr, err := parser.ParseExprTraditional(exprSpec.Expr)
if err != nil {
return nil, err
}
// Convert Placeholders to IndexedVars
v := valArgsConvert{h: h, err: nil}
expr, _ = parser.WalkExpr(&v, expr)
if v.err != nil {
return nil, v.err
}
// Convert to a fully typed expression.
typedExpr, err := parser.TypeCheck(expr, nil, parser.NoTypePreference)
if err != nil {
return nil, err
}
return typedExpr, nil
}
// exprHelper implements the common logic around evaluating an expression that
// depends on a set of values.
type exprHelper struct {
expr parser.TypedExpr
// vars is used to generate IndexedVars that are "backed" by
// the values in `row`.
vars parser.IndexedVarHelper
evalCtx *parser.EvalContext
types []sqlbase.ColumnType_Kind
row sqlbase.EncDatumRow
datumAlloc sqlbase.DatumAlloc
}
func (eh exprHelper) String() string {
if eh.expr == nil {
return "none"
}
return eh.expr.String()
}
// exprHelper implements parser.IndexedVarContainer.
var _ parser.IndexedVarContainer = &exprHelper{}
// IndexedVarReturnType is part of the parser.IndexedVarContainer interface.
func (eh *exprHelper) IndexedVarReturnType(idx int) parser.Datum {
return eh.types[idx].ToDatumType()
}
// IndexedVarEval is part of the parser.IndexedVarContainer interface.
func (eh *exprHelper) IndexedVarEval(idx int, ctx *parser.EvalContext) (parser.Datum, error) {
err := eh.row[idx].Decode(&eh.datumAlloc)
if err != nil {
return nil, err
}
return eh.row[idx].Datum.Eval(ctx)
}
// IndexedVarString is part of the parser.IndexedVarContainer interface.
func (eh *exprHelper) IndexedVarString(idx int) string {
return fmt.Sprintf("$%d", idx)
}
func (eh *exprHelper) init(
expr Expression, types []sqlbase.ColumnType_Kind, evalCtx *parser.EvalContext,
) error {
if expr.Expr == "" {
return nil
}
eh.types = types
eh.evalCtx = evalCtx
eh.vars = parser.MakeIndexedVarHelper(eh, len(types))
var err error
eh.expr, err = processExpression(expr, &eh.vars)
return err
}
// evalFilter is used for filter expressions; it evaluates the expression and
// returns whether the filter passes.
func (eh *exprHelper) evalFilter(row sqlbase.EncDatumRow) (bool, error) {
eh.row = row
return sqlbase.RunFilter(eh.expr, eh.evalCtx)
}