gitroast/vendor/github.com/pingcap/tidb/ast/ast.go

190 lines
6.2 KiB
Go

// Copyright 2015 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.
// Package ast is the abstract syntax tree parsed from a SQL statement by parser.
// It can be analysed and transformed by optimizer.
package ast
import (
"github.com/pingcap/tidb/context"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/util/types"
)
// Node is the basic element of the AST.
// Interfaces embed Node should have 'Node' name suffix.
type Node interface {
// Accept accepts Visitor to visit itself.
// The returned node should replace original node.
// ok returns false to stop visiting.
//
// Implementation of this method should first call visitor.Enter,
// assign the returned node to its method receiver, if skipChildren returns true,
// children should be skipped. Otherwise, call its children in particular order that
// later elements depends on former elements. Finally, return visitor.Leave.
Accept(v Visitor) (node Node, ok bool)
// Text returns the original text of the element.
Text() string
// SetText sets original text to the Node.
SetText(text string)
}
// Flags indicates whether an expression contains certain types of expression.
const (
FlagConstant uint64 = 0
FlagHasParamMarker uint64 = 1 << iota
FlagHasFunc
FlagHasReference
FlagHasAggregateFunc
FlagHasSubquery
FlagHasVariable
FlagHasDefault
)
// ExprNode is a node that can be evaluated.
// Name of implementations should have 'Expr' suffix.
type ExprNode interface {
// Node is embeded in ExprNode.
Node
// SetType sets evaluation type to the expression.
SetType(tp *types.FieldType)
// GetType gets the evaluation type of the expression.
GetType() *types.FieldType
// SetValue sets value to the expression.
SetValue(val interface{})
// GetValue gets value of the expression.
GetValue() interface{}
// SetDatum sets datum to the expression.
SetDatum(datum types.Datum)
// GetDatum gets datum of the expression.
GetDatum() *types.Datum
// SetFlag sets flag to the expression.
// Flag indicates whether the expression contains
// parameter marker, reference, aggregate function...
SetFlag(flag uint64)
// GetFlag returns the flag of the expression.
GetFlag() uint64
}
// FuncNode represents function call expression node.
type FuncNode interface {
ExprNode
functionExpression()
}
// StmtNode represents statement node.
// Name of implementations should have 'Stmt' suffix.
type StmtNode interface {
Node
statement()
}
// DDLNode represents DDL statement node.
type DDLNode interface {
StmtNode
ddlStatement()
}
// DMLNode represents DML statement node.
type DMLNode interface {
StmtNode
dmlStatement()
}
// ResultField represents a result field which can be a column from a table,
// or an expression in select field. It is a generated property during
// binding process. ResultField is the key element to evaluate a ColumnNameExpr.
// After resolving process, every ColumnNameExpr will be resolved to a ResultField.
// During execution, every row retrieved from table will set the row value to
// ResultFields of that table, so ColumnNameExpr resolved to that ResultField can be
// easily evaluated.
type ResultField struct {
Column *model.ColumnInfo
ColumnAsName model.CIStr
Table *model.TableInfo
TableAsName model.CIStr
DBName model.CIStr
// The expression for the result field. If it is generated from a select field, it would
// be the expression of that select field, otherwise the type would be ValueExpr and value
// will be set for every retrieved row.
Expr ExprNode
TableName *TableName
}
// Row represents a single row from Recordset.
type Row struct {
Data []types.Datum
}
// RecordSet is an abstract result set interface to help get data from Plan.
type RecordSet interface {
// Fields gets result fields.
Fields() (fields []*ResultField, err error)
// Next returns the next row, nil row means there is no more to return.
Next() (row *Row, err error)
// Close closes the underlying iterator, call Next after Close will
// restart the iteration.
Close() error
}
// ResultSetNode interface has ResultFields property which is computed and set by
// optimizer.InfoBinder during binding process. Implementations include SelectStmt,
// SubqueryExpr, TableSource, TableName and Join.
type ResultSetNode interface {
Node
// GetResultFields gets result fields of the result set node.
GetResultFields() []*ResultField
// SetResultFields sets result fields of the result set node.
SetResultFields(fields []*ResultField)
}
// Statement is an interface for SQL execution.
// NOTE: all Statement implementations must be safe for
// concurrent using by multiple goroutines.
// If the Exec method requires any Execution domain local data,
// they must be held out of the implementing instance.
type Statement interface {
// Explain gets the execution plans.
//Explain(ctx context.Context, w format.Formatter)
// IsDDL shows whether the statement is an DDL operation.
IsDDL() bool
// OriginText gets the origin SQL text.
OriginText() string
// SetText sets the executive SQL text.
SetText(text string)
// Exec executes SQL and gets a Recordset.
Exec(ctx context.Context) (RecordSet, error)
}
// Visitor visits a Node.
type Visitor interface {
// Enter is called before children nodes are visited.
// The returned node must be the same type as the input node n.
// skipChildren returns true means children nodes should be skipped,
// this is useful when work is done in Enter and there is no need to visit children.
Enter(n Node) (node Node, skipChildren bool)
// Leave is called after children nodes have been visited.
// The returned node's type can be different from the input node if it is a ExprNode,
// Non-expression node must be the same type as the input node n.
// ok returns false to stop visiting.
Leave(n Node) (node Node, ok bool)
}