execnodes.h

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 * Each executable expression tree has a parallel ExprState tree.
 *
 * Unlike PlanState, there is not an exact one-for-one correspondence between
 * ExprState node types and Expr node types.  Many Expr node types have no
 * need for node-type-specific run-time state, and so they can use plain
 * ExprState or GenericExprState as their associated ExprState node type.
 * ----------------------------------------------------------------
 */

/* ----------------
 *		ExprState node
 *
 * ExprState is the common superclass for all ExprState-type nodes.
 *
 * It can also be instantiated directly for leaf Expr nodes that need no
 * local run-time state (such as Var, Const, or Param).
 * ----------------
 */
typedef struct ExprState
{
	NodeTag		type;
	Expr	   *expr;			/* associated Expr node */
} ExprState;

/* ----------------
 *		GenericExprState node
 *
 * This is used for Expr node types that need no local run-time state,
 * but have one child Expr node.
 * ----------------
 */
typedef struct GenericExprState
{
	ExprState	xprstate;
	ExprState  *arg;			/* state of my child node */
} GenericExprState;

/* ----------------
 *		AggrefExprState node
 * ----------------
 */
typedef struct AggrefExprState
{
	ExprState	xprstate;
	ExprState  *target;			/* state of my child node */
	int			aggno;			/* ID number for agg within its plan node */
} AggrefExprState;

/* ----------------
 *		ArrayRefExprState node
 *
 * Note: array types can be fixed-length (typlen > 0), but only when the
 * element type is itself fixed-length.  Otherwise they are varlena structures
 * and have typlen = -1.  In any case, an array type is never pass-by-value.
 * ----------------
 */
typedef struct ArrayRefExprState
{
	ExprState	xprstate;
	List	   *refupperindexpr;	/* states for child nodes */
	List	   *reflowerindexpr;
	ExprState  *refexpr;
	ExprState  *refassgnexpr;
	int16		refattrlength;	/* typlen of array type */
	int16		refelemlength;	/* typlen of the array element type */
	bool		refelembyval;	/* is the element type pass-by-value? */
	char		refelemalign;	/* typalign of the element type */
} ArrayRefExprState;

/* ----------------
 *		FuncExprState node
 *
 * Although named for FuncExpr, this is also used for OpExpr, DistinctExpr,
 * and NullIf nodes; be careful to check what xprstate.expr is actually
 * pointing at!
 * ----------------
 */
typedef struct FuncExprState
{
	ExprState	xprstate;
	List	   *args;			/* states of argument expressions */

	/*
	 * Function manager's lookup info for the target function.  If
	 * func.fn_oid is InvalidOid, we haven't initialized it yet.
	 */
	FmgrInfo	func;

	/*
	 * We also need to store argument values across calls when evaluating
	 * a function-returning-set.
	 *
	 * setArgsValid is true when we are evaluating a set-valued function and
	 * we are in the middle of a call series; we want to pass the same
	 * argument values to the function again (and again, until it returns
	 * ExprEndResult).
	 */
	bool		setArgsValid;

	/*
	 * Flag to remember whether we found a set-valued argument to the
	 * function. This causes the function result to be a set as well.
	 * Valid only when setArgsValid is true.
	 */
	bool		setHasSetArg;	/* some argument returns a set */

	/*
	 * Flag to remember whether we have registered a shutdown callback for
	 * this FuncExprState.  We do so only if setArgsValid has been true at
	 * least once (since all the callback is for is to clear setArgsValid).
	 */
	bool		shutdown_reg;	/* a shutdown callback is registered */

	/*
	 * Current argument data for a set-valued function; contains valid
	 * data only if setArgsValid is true.
	 */
	FunctionCallInfoData setArgs;
} FuncExprState;

/* ----------------
 *		ScalarArrayOpExprState node
 *
 * This is a FuncExprState plus some additional data.
 * ----------------
 */
typedef struct ScalarArrayOpExprState
{
	FuncExprState fxprstate;
	/* Cached info about array element type */
	Oid			element_type;
	int16		typlen;
	bool		typbyval;
	char		typalign;
} ScalarArrayOpExprState;

/* ----------------
 *		BoolExprState node
 * ----------------
 */
typedef struct BoolExprState
{
	ExprState	xprstate;
	List	   *args;			/* states of argument expression(s) */
} BoolExprState;

/* ----------------
 *		SubPlanState node
 * ----------------
 */
typedef struct SubPlanState
{
	ExprState	xprstate;
	EState	   *sub_estate;		/* subselect plan has its own EState */
	struct PlanState *planstate;	/* subselect plan's state tree */
	List	   *exprs;			/* states of combining expression(s) */
	List	   *args;			/* states of argument expression(s) */
	bool		needShutdown;	/* TRUE = need to shutdown subplan */
	HeapTuple	curTuple;		/* copy of most recent tuple from subplan */
	/* these are used when hashing the subselect's output: */
	ProjectionInfo *projLeft;	/* for projecting lefthand exprs */
	ProjectionInfo *projRight;	/* for projecting subselect output */
	TupleHashTable hashtable;	/* hash table for no-nulls subselect rows */
	TupleHashTable hashnulls;	/* hash table for rows with null(s) */
	bool		havehashrows;	/* TRUE if hashtable is not empty */
	bool		havenullrows;	/* TRUE if hashnulls is not empty */
	MemoryContext tablecxt;		/* memory context containing tables */
	ExprContext *innerecontext; /* working context for comparisons */
	AttrNumber *keyColIdx;		/* control data for hash tables */
	FmgrInfo   *eqfunctions;	/* comparison functions for hash tables */
	FmgrInfo   *hashfunctions;	/* lookup data for hash functions */
} SubPlanState;

/* ----------------
 *		CaseExprState node
 * ----------------
 */
typedef struct CaseExprState
{
	ExprState	xprstate;
	List	   *args;			/* the arguments (list of WHEN clauses) */
	ExprState  *defresult;		/* the default result (ELSE clause) */
} CaseExprState;

/* ----------------
 *		CaseWhenState node
 * ----------------
 */
typedef struct CaseWhenState
{
	ExprState	xprstate;
	ExprState  *expr;			/* condition expression */
	ExprState  *result;			/* substitution result */
} CaseWhenState;

/* ----------------
 *		ArrayExprState node
 *
 * Note: ARRAY[] expressions always produce varlena arrays, never fixed-length
 * arrays.
 * ----------------
 */
typedef struct ArrayExprState
{
	ExprState	xprstate;
	List	   *elements;		/* states for child nodes */
	int16		elemlength;		/* typlen of the array element type */
	bool		elembyval;		/* is the element type pass-by-value? */
	char		elemalign;		/* typalign of the element type */
} ArrayExprState;

/* ----------------
 *		CoalesceExprState node
 * ----------------
 */
typedef struct CoalesceExprState
{
	ExprState	xprstate;
	List	   *args;			/* the arguments */
} CoalesceExprState;

/* ----------------
 *		CoerceToDomainState node
 * ----------------
 */
typedef struct CoerceToDomainState
{
	ExprState	xprstate;
	ExprState  *arg;			/* input expression */
	/* Cached list of constraints that need to be checked */
	List	   *constraints;	/* list of DomainConstraintState nodes */
} CoerceToDomainState;

/*
 * DomainConstraintState - one item to check during CoerceToDomain
 *
 * Note: this is just a Node, and not an ExprState, because it has no
 * corresponding Expr to link to.  Nonetheless it is part of an ExprState
 * tree, so we give it a name following the xxxState convention.
 */
typedef enum DomainConstraintType
{
	DOM_CONSTRAINT_NOTNULL,
	DOM_CONSTRAINT_CHECK
} DomainConstraintType;

typedef struct DomainConstraintState
{
	NodeTag		type;
	DomainConstraintType constrainttype;		/* constraint type */
	char	   *name;			/* name of constraint (for error msgs) */
	ExprState  *check_expr;		/* for CHECK, a boolean expression */
} DomainConstraintState;


/* ----------------------------------------------------------------
 *				 Executor State Trees
 *
 * An executing query has a PlanState tree paralleling the Plan tree
 * that describes the plan.
 * ----------------------------------------------------------------
 */

/* ----------------
 *		PlanState node
 *
 * We never actually instantiate any PlanState nodes; this is just the common
 * abstract superclass for all PlanState-type nodes.
 * ----------------
 */
typedef struct PlanState
{
	NodeTag		type;

	Plan	   *plan;			/* associated Plan node */

	EState	   *state;			/* at execution time, state's of
								 * individual nodes point to one EState
								 * for the whole top-level plan */

	struct Instrumentation *instrument; /* Optional runtime stats for this
										 * plan node */

	/*
	 * Common structural data for all Plan types.  These links to
	 * subsidiary state trees parallel links in the associated plan tree
	 * (except for the subPlan list, which does not exist in the plan
	 * tree).
	 */
	List	   *targetlist;		/* target list to be computed at this node */
	List	   *qual;			/* implicitly-ANDed qual conditions */
	struct PlanState *lefttree; /* input plan tree(s) */
	struct PlanState *righttree;
	List	   *initPlan;		/* Init SubPlanState nodes (un-correlated
								 * expr subselects) */
	List	   *subPlan;		/* SubPlanState nodes in my expressions */

	/*
	 * State for management of parameter-change-driven rescanning
	 */
	Bitmapset  *chgParam;		/* set of IDs of changed Params */

	/*
	 * Other run-time state needed by most if not all node types.
	 */
	TupleTableSlot *ps_OuterTupleSlot;	/* slot for current "outer" tuple */
	TupleTableSlot *ps_ResultTupleSlot; /* slot for my result tuples */
	ExprContext *ps_ExprContext;	/* node's expression-evaluation context */
	ProjectionInfo *ps_ProjInfo;	/* info for doing tuple projection */
	bool		ps_TupFromTlist;/* state flag for processing set-valued
								 * functions in targetlist */
} PlanState;

/* ----------------
 *	these are are defined to avoid confusion problems with "left"
 *	and "right" and "inner" and "outer".  The convention is that
 *	the "left" plan is the "outer" plan and the "right" plan is
 *	the inner plan, but these make the code more readable.
 * ----------------
 */
#define innerPlanState(node)		(((PlanState *)(node))->righttree)
#define outerPlanState(node)		(((PlanState *)(node))->lefttree)


/* ----------------
 *	 ResultState information
 * ----------------
 */
typedef struct ResultState
{
	PlanState	ps;				/* its first field is NodeTag */
	ExprState  *resconstantqual;
	bool		rs_done;		/* are we done? */
	bool		rs_checkqual;	/* do we need to check the qual? */
} ResultState;

/* ----------------
 *	 AppendState information
 *
 *		nplans			how many plans are in the list
 *		whichplan		which plan is being executed (0 .. n-1)
 *		firstplan		first plan to execute (usually 0)
 *		lastplan		last plan to execute (usually n-1)
 * ----------------
 */
typedef struct AppendState
{
	PlanState	ps;				/* its first field is NodeTag */
	PlanState **appendplans;	/* array of PlanStates for my inputs */
	int			as_nplans;
	int			as_whichplan;
	int			as_firstplan;
	int			as_lastplan;
} AppendState;

/* ----------------------------------------------------------------
 *				 Scan State Information
 * ----------------------------------------------------------------
 */

/* ----------------
 *	 ScanState information
 *
 *		ScanState extends PlanState for node types that represent
 *		scans of an underlying relation.  It can also be used for nodes
 *		that scan the output of an underlying plan node --- in that case,
 *		only ScanTupleSlot is actually useful, and it refers to the tuple
 *		retrieved from the subplan.
 *
 *		currentRelation    relation being scanned (NULL if none)
 *		currentScanDesc    current scan descriptor for scan (NULL if none)
 *		ScanTupleSlot	   pointer to slot in tuple table holding scan tuple
 * ----------------
 */
typedef struct ScanState
{