forked from cockroachdb/cockroach
/
placeholders.go
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/
placeholders.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 parser
import "fmt"
// PlaceholderTypes relates placeholder names to their resolved type.
type PlaceholderTypes map[string]Datum
// QueryArguments relates placeholder names to their provided query argument.
type QueryArguments map[string]Datum
// PlaceholderInfo defines the interface to SQL placeholders.
type PlaceholderInfo struct {
Values QueryArguments
Types PlaceholderTypes
}
// NewPlaceholderInfo constructs an empty PlaceholderInfo.
func NewPlaceholderInfo() *PlaceholderInfo {
res := &PlaceholderInfo{}
res.Clear()
return res
}
// Clear resets the placeholder info map.
func (p *PlaceholderInfo) Clear() {
p.Types = PlaceholderTypes{}
p.Values = QueryArguments{}
}
// Assign resets the PlaceholderInfo to the contents of src.
// If src is nil, the map is cleared.
func (p *PlaceholderInfo) Assign(src *PlaceholderInfo) {
if src != nil {
*p = *src
} else {
p.Clear()
}
}
// Type returns the known type of a placeholder.
// Returns false in the 2nd value if the placeholder is not typed.
func (p *PlaceholderInfo) Type(name string) (Datum, bool) {
if t, ok := p.Types[name]; ok {
return t, true
}
return nil, false
}
// Value returns the known value of a placeholder. Returns false in
// the 2nd value if the placeholder does not have a value.
func (p *PlaceholderInfo) Value(name string) (Datum, bool) {
if v, ok := p.Values[name]; ok {
return v, true
}
return nil, false
}
// SetValue assigns a known value to a placeholder.
// If no type is known yet, it is inferred from the assigned value.
func (p *PlaceholderInfo) SetValue(name string, val Datum) {
if _, ok := p.Values[name]; ok {
panic(fmt.Sprintf("placeholder $%s already has a value", name))
}
p.Values[name] = val
if _, ok := p.Types[name]; !ok {
// No type yet, infer from value
p.Types[name] = val.ReturnType()
}
}
// SetType assignes a known type to a placeholder.
// Reports an error if another type was previously assigned.
func (p *PlaceholderInfo) SetType(name string, typ Datum) error {
if t, ok := p.Types[name]; ok && !typ.TypeEqual(t) {
return fmt.Errorf("placeholder %s already has type %s, cannot assign %s", name, t.Type(), typ.Type())
}
p.Types[name] = typ
return nil
}
// SetTypes resets the type and values in the map and replaces the
// types map by an alias to src. If src is nil, the map is cleared.
// The types map is aliased because the invoking code from
// pgwire/v3.go for sql.Prepare needs to receive the updated type
// assignments after Prepare completes.
func (p *PlaceholderInfo) SetTypes(src PlaceholderTypes) {
if src != nil {
p.Types = src
p.Values = QueryArguments{}
} else {
p.Clear()
}
}
// IsUnresolvedPlaceholder returns whether expr is an unresolved placeholder. In
// other words, it returns whether the provided expression is a placeholder
// expression or a placeholder expression within nested parentheses, and if so,
// whether the placeholder's type remains unset in the PlaceholderInfo.
func (p *PlaceholderInfo) IsUnresolvedPlaceholder(expr Expr) bool {
if t, ok := StripParens(expr).(Placeholder); ok {
_, res := p.Types[t.Name]
return !res
}
return false
}