plan

type Aggregation struct {
	Op    int     //  opcode of aggregation function
	Ref   int     // reference count
	Type  types.T //  return type of aggregation function
	Name  string  //  name of attribute
	Alias string
	E     extend.Extend
}

type Attribute struct {
	Ref  int        // reference count
	Name string     // name of attribute
	Type types.Type // type of attribute
}

type CreateDatabase struct {
	IfNotExistFlag bool
	Id             string
	E              engine.Engine
}

type CreateIndex struct {
	IfNotExistFlag bool
	HasExist       bool // if true, means this index has existed.
	Id             string
	Relation       engine.Relation
	Defs           []engine.TableDef
}

type CreateTable struct {
	IfNotExistFlag bool
	Id             string
	Db             engine.Database
	Defs           []engine.TableDef
	PartitionBy    *engine.PartitionByDef
}

type Dedup struct {
}

type Delete struct {
	Qry *Query
}

type DerivedRelation struct {
	Proj Projection
	Cond extend.Extend

	Flg       bool // indicate if transform is required
	FreeVars  []string
	BoundVars []*Aggregation
}

type Direction int8

type DropDatabase struct {
	IfExistFlag bool
	Id          string
	E           engine.Engine
}

type DropIndex struct {
	IfExistFlag bool
	NotExisted  bool // if true, means this index does not exist.
	Id          string
	Relation    engine.Relation
}

type DropTable struct {
	IfExistFlag bool
	Ids         []string
	Dbs         []string
	E           engine.Engine
}

type Edge struct {
	Vs []int
}

type EdgeSet struct {
	W      int // weight
	I1, I2 int // subscript for E1 and E2
	E1, E2 *Edge
}

type Field struct {
	Attr string
	Type Direction
}

type Graph struct {
	Es []*Edge
}

type Insert struct {
	Id       string
	Db       string
	Bat      *batch.Batch
	Relation engine.Relation
}

type Join struct {
	Type   int // join type
	Vars   [][]int
	Result []string
}

type JoinCondition struct {
	R     int
	S     int
	Rattr string
	Sattr string

	Alias int
}

type Limit struct {
	Limit int64
}

type Offset struct {
	Offset int64
}

type Order struct {
	Fs []*Field
}

type Plan interface {
	fmt.Stringer
	ResultColumns() []*Attribute
}

type Projection struct {
	Rs []uint64 // reference count list
	As []string // alias name list
	Es []extend.Extend
}

type Query struct {
	Flg        bool // rebuild flag
	Scope      *Scope
	Result     []string
	Stack      []*ScopeSet
	Aggs       []*Aggregation
	RenameRels map[string]*Scope
	Rels       map[string]map[string]*Scope

	Children []*Scope // subquery
}

type Relation struct {
	Rows   int64
	Name   string                // table name
	Schema string                // schema name
	Attrs  map[string]*Attribute // table's column information

	Flg  bool // indicate if transform is required
	Proj Projection
	Cond extend.Extend

	FreeVars  []string
	BoundVars []*Aggregation
}

type Rename struct {
	Rs []uint64 // reference count list
	As []string // alias name list
	Es []extend.Extend
}

type Restrict struct {
	E extend.Extend
}

type ResultAttributes struct {
	Attrs    []string
	AttrsMap map[string]*Attribute
}

type ResultProjection struct {
	Rs []uint64 // reference count list
	As []string // alias name list
	Es []extend.Extend
}

type Scope struct {
	Name     string
	Children []*Scope
	Op       interface{}
	Result   ResultAttributes
}

type ScopeSet struct {
	JoinType int
	Scopes   []*Scope
	Conds    []*JoinCondition
}

type ShowColumns struct {
	Relation engine.Relation
	Like     []byte
}

type ShowCreateDatabase struct {
	IfNotExistFlag bool
	Id             string
	E              engine.Engine
}

type ShowCreateTable struct {
	Relation  engine.Relation
	TableName string
}

type ShowDatabases struct {
	E    engine.Engine
	Like []byte
}

type ShowTables struct {
	Db   engine.Database
	Like []byte
}

type SymbolTable struct {
	Entries map[string]*Attribute
}

type Untransform struct {
	FreeVars []string
}

type Update struct {
	Qry         *Query
	UpdateList  []extend.UpdateExtend
	UpdateAttrs []string
	OtherAttrs  []string
}

type VertexSet struct {
	Is []int
	Es []*Edge
}