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statement_select.go
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statement_select.go
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// Copyright (c) 2013 Couchbase, Inc.
// 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 ast
import (
"fmt"
)
type SelectStatement struct {
Distinct bool `json:"distinct"`
Select ResultExpressionList `json:"select"`
From *From `json:"from"`
Where Expression `json:"where"`
GroupBy ExpressionList `json:"group_by"`
Having Expression `json:"having"`
OrderBy SortExpressionList `json:"orderby"`
Limit int `json:"limit"`
Offset int `json:"offset"`
ExplainOnly bool `json:"explain"`
Keys *KeyExpression `json:"keys"`
explicitProjectionAliases []string
aggregateReferences ExpressionList
}
func NewSelectStatement() *SelectStatement {
return &SelectStatement{
Limit: -1,
}
}
func (this *SelectStatement) GetFromAliases() []string {
if this.From != nil {
return this.From.GetAliases()
}
return []string{}
}
func (this *SelectStatement) GetFrom() *From {
return this.From
}
func (this *SelectStatement) GetWhere() Expression {
return this.Where
}
func (this *SelectStatement) GetGroupBy() ExpressionList {
return this.GroupBy
}
func (this *SelectStatement) GetHaving() Expression {
return this.Having
}
func (this *SelectStatement) GetOrderBy() SortExpressionList {
return this.OrderBy
}
func (this *SelectStatement) GetLimit() int {
return this.Limit
}
func (this *SelectStatement) GetOffset() int {
return this.Offset
}
func (this *SelectStatement) IsDistinct() bool {
return this.Distinct
}
func (this *SelectStatement) GetResultExpressionList() ResultExpressionList {
return this.Select
}
func (this *SelectStatement) SetExplainOnly(explainOnly bool) {
this.ExplainOnly = explainOnly
}
func (this *SelectStatement) IsExplainOnly() bool {
return this.ExplainOnly
}
func (this *SelectStatement) GetExplicitProjectionAliases() []string {
return this.explicitProjectionAliases
}
func (this *SelectStatement) GetAggregateReferences() ExpressionList {
return this.aggregateReferences
}
func (this *SelectStatement) IsAggregate() bool {
if this.GroupBy != nil {
return true
}
// now check the projection for any aggregate functions
return this.Select.ContainsAggregateFunctionCall()
}
func (this *SelectStatement) VerifySemantics() error {
var err error
// get the list of explicit projection aliases, and check it for duplicates
this.explicitProjectionAliases, err = this.Select.CheckForDuplicateAliases()
if err != nil {
return err
}
// now apply default naming function
err = this.Select.AssignDefaultNames(this.explicitProjectionAliases)
if err != nil {
return err
}
// fix up all the froms (FIXME need to refactor this into FROM/OVER clenaup)
if this.From != nil {
this.From.ConvertToBucketFrom()
this.From.GenerateAlias()
}
if this.From != nil {
nextOver := this.From.Over
for nextOver != nil {
// If Keys is present then this is a key-join,
// and we need to make sure that the from clause contains a bucket
if nextOver.Keys != nil {
nextOver.ConvertToBucketFrom()
}
nextOver = nextOver.Over
}
}
// verify formal notations
err = this.verifyFormalNotation(this.explicitProjectionAliases)
if err != nil {
return err
}
// validate the expressions
err = this.validate()
if err != nil {
return err
}
// if this is an aggregate query we need to perform some additional checks
if this.IsAggregate() {
// valid order by expressions
validOrderByExpressions := ExpressionList{}
if this.GroupBy != nil {
for _, gb := range this.GroupBy {
validOrderByExpressions = append(validOrderByExpressions, gb)
}
}
for _, alias := range this.explicitProjectionAliases {
validOrderByExpressions = append(validOrderByExpressions, NewProperty(alias))
}
// separate two cases, with group by and without
if this.GroupBy == nil {
// this means an aggregate function was used, but there was no group by
// in this case, all projection expressions MUST be aggregate function calls
err := this.Select.VerifyAllAggregateFunctionsOrInThisList(ExpressionList{})
if err != nil {
return err
}
if this.Having != nil {
fdc := NewExpressionFunctionalDependencyChecker(ExpressionList{})
_, err := this.Having.Accept(fdc)
if err != nil {
return err
}
}
if this.OrderBy != nil {
err := this.OrderBy.VerifyAllAggregateFunctionsOrInThisList(validOrderByExpressions)
if err != nil {
return err
}
}
// set group by to an empty expresison list
// the group will use this to behave correctly
this.GroupBy = ExpressionList{}
} else {
// ensure that all projection expressions are either aggregate functipn calls
// or in the group by expression list
err := this.Select.VerifyAllAggregateFunctionsOrInThisList(this.GroupBy)
if err != nil {
return err
}
if this.Having != nil {
fdc := NewExpressionFunctionalDependencyChecker(this.GroupBy)
_, err := this.Having.Accept(fdc)
if err != nil {
return err
}
}
if this.OrderBy != nil {
err := this.OrderBy.VerifyAllAggregateFunctionsOrInThisList(validOrderByExpressions)
if err != nil {
return err
}
}
}
// gather the aggregate references and store these
this.aggregateReferences = this.findAggregateFunctionReferences()
}
// if you combine DISTINCT with ORDER BY we have to do an additional validation
if this.Distinct && this.OrderBy != nil {
// every Order By expression MUST be equivalent to one in the projection
err := this.OrderBy.VerifyAllEquivalentToThisList(this.Select.ExpressionList())
if err != nil {
return err
}
}
return nil
}
func (this *SelectStatement) validate() error {
// validate the projection
err := this.Select.Validate()
if err != nil {
return err
}
// validate the where
if this.Where != nil {
whereValidator := NewExpressionValidatorNoAggregates()
this.Where, err = this.Where.Accept(whereValidator)
if err != nil {
return err
}
}
// validate the From clause
if this.From != nil {
aliases := this.From.GetAliases()
fromOver := this.From.Over
for fromOver != nil {
if fromOver.Keys != nil {
err = fromOver.Keys.Validate()
if err != nil {
return err
}
} else {
err = fromOver.VerifyBucket(aliases)
if err != nil {
return err
}
}
fromOver = fromOver.Over
}
}
if this.Keys != nil {
err = this.Keys.Validate()
if err != nil {
return err
}
if len(this.Keys.GetKeys()) == 0 {
return fmt.Errorf("KEY clause contains an invalid expression")
}
}
// validate the order by
err = this.OrderBy.Validate()
if err != nil {
return err
}
// validate the group by
if this.GroupBy != nil {
err = this.GroupBy.Validate()
if err != nil {
return err
}
}
// validate the having
if this.Having != nil {
havingValidator := NewExpressionValidator()
this.Having, err = this.Having.Accept(havingValidator)
if err != nil {
return err
}
}
return nil
}
func (this *SelectStatement) verifyFormalNotation(explicitProjectionAliases []string) error {
// gather the list of aliases
aliases := this.GetFromAliases()
defaultAlias := ""
if len(aliases) == 1 {
defaultAlias = aliases[0]
}
formalNotation := NewExpressionFormalNotationConverter(explicitProjectionAliases, aliases, defaultAlias)
// verify the projection (references to projection aliases not allowed)
err := this.Select.VerifyFormalNotation(explicitProjectionAliases, aliases, defaultAlias)
if err != nil {
return err
}
// verify the where (references to projection aliases not allowed)
if this.Where != nil {
this.Where, err = this.Where.Accept(formalNotation)
if err != nil {
return err
}
}
if this.Keys != nil {
this.Keys.Expr, err = this.Keys.Expr.Accept(formalNotation)
if err != nil {
return err
}
}
// verify the order by(references to projection aliases ARE allowed)
// since order by CAN reference the explicit aliases, these must be added to the list
// passed into this phase
orderByAliases := make([]string, 0)
for _, alias := range aliases {
orderByAliases = append(orderByAliases, alias)
}
for _, alias := range explicitProjectionAliases {
orderByAliases = append(orderByAliases, alias)
}
err = this.OrderBy.VerifyFormalNotation([]string{}, orderByAliases, defaultAlias)
if err != nil {
return err
}
// verify the group by (references to projection aliases not allowed)
if this.GroupBy != nil {
err = this.GroupBy.VerifyFormalNotation(explicitProjectionAliases, aliases, defaultAlias)
if err != nil {
return err
}
}
// verify the having (references to projection aliases not allowed)
if this.Having != nil {
this.Having, err = this.Having.Accept(formalNotation)
if err != nil {
return err
}
}
return nil
}
// SELECT, HAVING, and ORDER BY may all reference aggregate functions
// we need to find these so that we can produce the appropriate stats
// during the grouping phase
func (this *SelectStatement) findAggregateFunctionReferences() ExpressionList {
ar := this.Select.findAggregateFunctionReferences()
if this.Having != nil {
af := NewExpressionAggregateFinder()
this.Having.Accept(af)
havingRefs := af.GetAggregates()
if len(havingRefs) > 0 {
ar = append(ar, havingRefs...)
}
}
if this.OrderBy != nil {
orderRefs := this.OrderBy.findAggregateFunctionReferences()
if len(orderRefs) > 0 {
ar = append(ar, orderRefs...)
}
}
//finally we need to remove duplicates from this list
for i, agga := range ar {
if agga != nil {
for j, aggb := range ar[i+1:] {
if aggb != nil {
if agga.EquivalentTo(aggb) {
ar[i+j+1] = nil
}
}
}
}
}
rv := make(ExpressionList, 0)
for _, agg := range ar {
if agg != nil {
rv = append(rv, agg)
}
}
return rv
}
func (this *SelectStatement) Simplify() error {
err := this.Select.Simplify()
if err != nil {
return err
}
if this.Where != nil {
es := NewExpressionSimplifier()
this.Where, err = this.Where.Accept(es)
if err != nil {
return err
}
}
if this.Keys != nil {
es := NewExpressionSimplifier()
this.Keys.Expr, err = this.Keys.Expr.Accept(es)
if err != nil {
return err
}
}
// simplify the order by
err = this.OrderBy.Simplify()
if err != nil {
return err
}
// simplify the group by
if this.GroupBy != nil {
err = this.GroupBy.Simplify()
if err != nil {
return err
}
}
// simlify the having
if this.Having != nil {
es := NewExpressionSimplifier()
this.Having, err = this.Having.Accept(es)
if err != nil {
return err
}
}
return nil
}