postgresql/src/include/nodes/nodes.h

/*-------------------------------------------------------------------------
 *
 * nodes.h
 *	  Definitions for tagged nodes.
 *
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/nodes/nodes.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef NODES_H
#define NODES_H

/*
 * The first field of every node is NodeTag. Each node created (with makeNode)
 * will have one of the following tags as the value of its first field.
 *
 * Note that inserting or deleting node types changes the numbers of other
 * node types later in the list.  This is no problem during development, since
 * the node numbers are never stored on disk.  But don't do it in a released
 * branch, because that would represent an ABI break for extensions.
 */
typedef enum NodeTag
{
	T_Invalid = 0,

#include "nodes/nodetags.h"
} NodeTag;

/*
 * pg_node_attr() - Used in node definitions to set extra information for
 * gen_node_support.pl
 *
 * Attributes can be attached to a node as a whole (place the attribute
 * specification on the first line after the struct's opening brace)
 * or to a specific field (place it at the end of that field's line).  The
 * argument is a comma-separated list of attributes.  Unrecognized attributes
 * cause an error.
 *
 * Valid node attributes:
 *
 * - abstract: Abstract types are types that cannot be instantiated but that
 *   can be supertypes of other types.  We track their fields, so that
 *   subtypes can use them, but we don't emit a node tag, so you can't
 *   instantiate them.
 *
 * - custom_copy_equal: Has custom implementations in copyfuncs.c and
 *   equalfuncs.c.
 *
 * - custom_read_write: Has custom implementations in outfuncs.c and
 *   readfuncs.c.
 *
 * - no_copy: Does not support copyObject() at all.
 *
 * - no_equal: Does not support equal() at all.
 *
 * - no_copy_equal: Shorthand for both no_copy and no_equal.
 *
 * - no_read: Does not support nodeRead() at all.
 *
 * - nodetag_only: Does not support copyObject(), equal(), outNode(),
 *   or nodeRead().
 *
 * - special_read_write: Has special treatment in outNode() and nodeRead().
 *
 * - nodetag_number(VALUE): assign the specified nodetag number instead of
 *   an auto-generated number.  Typically this would only be used in stable
 *   branches, to give a newly-added node type a number without breaking ABI
 *   by changing the numbers of existing node types.
 *
 * Node types can be supertypes of other types whether or not they are marked
 * abstract: if a node struct appears as the first field of another struct
 * type, then it is the supertype of that type.  The no_copy, no_equal, and
 * no_read node attributes are automatically inherited from the supertype.
 * (Notice that nodetag_only does not inherit, so it's not quite equivalent
 * to a combination of other attributes.)
 *
 * Valid node field attributes:
 *
 * - array_size(OTHERFIELD): This field is a dynamically allocated array with
 *   size indicated by the mentioned other field.  The other field is either a
 *   scalar or a list, in which case the length of the list is used.
 *
 * - copy_as(VALUE): In copyObject(), replace the field's value with VALUE.
 *
 * - equal_ignore: Ignore the field for equality.
 *
 * - equal_ignore_if_zero: Ignore the field for equality if it is zero.
 *   (Otherwise, compare normally.)
 *
 * - read_as(VALUE): In nodeRead(), replace the field's value with VALUE.
 *
 * - read_write_ignore: Ignore the field for read/write.  This is only allowed
 *   if the node type is marked no_read or read_as() is also specified.
 *
 * - write_only_relids, write_only_nondefault_pathtarget, write_only_req_outer:
 *   Special handling for Path struct; see there.
 *
 */
#define pg_node_attr(...)

/*
 * The first field of a node of any type is guaranteed to be the NodeTag.
 * Hence the type of any node can be gotten by casting it to Node. Declaring
 * a variable to be of Node * (instead of void *) can also facilitate
 * debugging.
 */
typedef struct Node
{
	NodeTag		type;
} Node;

#define nodeTag(nodeptr)		(((const Node*)(nodeptr))->type)

/*
 * newNode -
 *	  create a new node of the specified size and tag the node with the
 *	  specified tag.
 *
 * !WARNING!: Avoid using newNode directly. You should be using the
 *	  macro makeNode.  eg. to create a Query node, use makeNode(Query)
 *
 * Note: the size argument should always be a compile-time constant, so the
 * apparent risk of multiple evaluation doesn't matter in practice.
 */
#ifdef __GNUC__

/* With GCC, we can use a compound statement within an expression */
#define newNode(size, tag) \
({	Node   *_result; \
	AssertMacro((size) >= sizeof(Node));		/* need the tag, at least */ \
	_result = (Node *) palloc0fast(size); \
	_result->type = (tag); \
	_result; \
})
#else

/*
 *	There is no way to dereference the palloc'ed pointer to assign the
 *	tag, and also return the pointer itself, so we need a holder variable.
 *	Fortunately, this macro isn't recursive so we just define
 *	a global variable for this purpose.
 */
extern PGDLLIMPORT Node *newNodeMacroHolder;

#define newNode(size, tag) \
( \
	AssertMacro((size) >= sizeof(Node)),		/* need the tag, at least */ \
	newNodeMacroHolder = (Node *) palloc0fast(size), \
	newNodeMacroHolder->type = (tag), \
	newNodeMacroHolder \
)
#endif							/* __GNUC__ */


#define makeNode(_type_)		((_type_ *) newNode(sizeof(_type_),T_##_type_))
#define NodeSetTag(nodeptr,t)	(((Node*)(nodeptr))->type = (t))

#define IsA(nodeptr,_type_)		(nodeTag(nodeptr) == T_##_type_)

/*
 * castNode(type, ptr) casts ptr to "type *", and if assertions are enabled,
 * verifies that the node has the appropriate type (using its nodeTag()).
 *
 * Use an inline function when assertions are enabled, to avoid multiple
 * evaluations of the ptr argument (which could e.g. be a function call).
 */
#ifdef USE_ASSERT_CHECKING
static inline Node *
castNodeImpl(NodeTag type, void *ptr)
{
	Assert(ptr == NULL || nodeTag(ptr) == type);
	return (Node *) ptr;
}
#define castNode(_type_, nodeptr) ((_type_ *) castNodeImpl(T_##_type_, nodeptr))
#else
#define castNode(_type_, nodeptr) ((_type_ *) (nodeptr))
#endif							/* USE_ASSERT_CHECKING */


/* ----------------------------------------------------------------
 *					  extern declarations follow
 * ----------------------------------------------------------------
 */

/*
 * nodes/{outfuncs.c,print.c}
 */
struct Bitmapset;				/* not to include bitmapset.h here */
struct StringInfoData;			/* not to include stringinfo.h here */

extern void outNode(struct StringInfoData *str, const void *obj);
extern void outToken(struct StringInfoData *str, const char *s);
extern void outBitmapset(struct StringInfoData *str,
						 const struct Bitmapset *bms);
extern void outDatum(struct StringInfoData *str, uintptr_t value,
					 int typlen, bool typbyval);
extern char *nodeToString(const void *obj);
extern char *bmsToString(const struct Bitmapset *bms);

/*
 * nodes/{readfuncs.c,read.c}
 */
extern void *stringToNode(const char *str);
#ifdef WRITE_READ_PARSE_PLAN_TREES
extern void *stringToNodeWithLocations(const char *str);
#endif
extern struct Bitmapset *readBitmapset(void);
extern uintptr_t readDatum(bool typbyval);
extern bool *readBoolCols(int numCols);
extern int *readIntCols(int numCols);
extern Oid *readOidCols(int numCols);
extern int16 *readAttrNumberCols(int numCols);

/*
 * nodes/copyfuncs.c
 */
extern void *copyObjectImpl(const void *obj);

/* cast result back to argument type, if supported by compiler */
#ifdef HAVE_TYPEOF
#define copyObject(obj) ((typeof(obj)) copyObjectImpl(obj))
#else
#define copyObject(obj) copyObjectImpl(obj)
#endif

/*
 * nodes/equalfuncs.c
 */
extern bool equal(const void *a, const void *b);


/*
 * Typedefs for identifying qualifier selectivities and plan costs as such.
 * These are just plain "double"s, but declaring a variable as Selectivity
 * or Cost makes the intent more obvious.
 *
 * These could have gone into plannodes.h or some such, but many files
 * depend on them...
 */
typedef double Selectivity;		/* fraction of tuples a qualifier will pass */
typedef double Cost;			/* execution cost (in page-access units) */
typedef double Cardinality;		/* (estimated) number of rows or other integer
								 * count */


/*
 * CmdType -
 *	  enums for type of operation represented by a Query or PlannedStmt
 *
 * This is needed in both parsenodes.h and plannodes.h, so put it here...
 */
typedef enum CmdType
{
	CMD_UNKNOWN,
	CMD_SELECT,					/* select stmt */
	CMD_UPDATE,					/* update stmt */
	CMD_INSERT,					/* insert stmt */
	CMD_DELETE,					/* delete stmt */
	CMD_MERGE,					/* merge stmt */
	CMD_UTILITY,				/* cmds like create, destroy, copy, vacuum,
								 * etc. */
	CMD_NOTHING					/* dummy command for instead nothing rules
								 * with qual */
} CmdType;


/*
 * JoinType -
 *	  enums for types of relation joins
 *
 * JoinType determines the exact semantics of joining two relations using
 * a matching qualification.  For example, it tells what to do with a tuple
 * that has no match in the other relation.
 *
 * This is needed in both parsenodes.h and plannodes.h, so put it here...
 */
typedef enum JoinType
{
	/*
	 * The canonical kinds of joins according to the SQL JOIN syntax. Only
	 * these codes can appear in parser output (e.g., JoinExpr nodes).
	 */
	JOIN_INNER,					/* matching tuple pairs only */
	JOIN_LEFT,					/* pairs + unmatched LHS tuples */
	JOIN_FULL,					/* pairs + unmatched LHS + unmatched RHS */
	JOIN_RIGHT,					/* pairs + unmatched RHS tuples */

	/*
	 * Semijoins and anti-semijoins (as defined in relational theory) do not
	 * appear in the SQL JOIN syntax, but there are standard idioms for
	 * representing them (e.g., using EXISTS).  The planner recognizes these
	 * cases and converts them to joins.  So the planner and executor must
	 * support these codes.  NOTE: in JOIN_SEMI output, it is unspecified
	 * which matching RHS row is joined to.  In JOIN_ANTI output, the row is
	 * guaranteed to be null-extended.
	 */
	JOIN_SEMI,					/* 1 copy of each LHS row that has match(es) */
	JOIN_ANTI,					/* 1 copy of each LHS row that has no match */

	/*
	 * These codes are used internally in the planner, but are not supported
	 * by the executor (nor, indeed, by most of the planner).
	 */
	JOIN_UNIQUE_OUTER,			/* LHS path must be made unique */
	JOIN_UNIQUE_INNER			/* RHS path must be made unique */

	/*
	 * We might need additional join types someday.
	 */
} JoinType;

/*
 * OUTER joins are those for which pushed-down quals must behave differently
 * from the join's own quals.  This is in fact everything except INNER and
 * SEMI joins.  However, this macro must also exclude the JOIN_UNIQUE symbols
 * since those are temporary proxies for what will eventually be an INNER
 * join.
 *
 * Note: semijoins are a hybrid case, but we choose to treat them as not
 * being outer joins.  This is okay principally because the SQL syntax makes
 * it impossible to have a pushed-down qual that refers to the inner relation
 * of a semijoin; so there is no strong need to distinguish join quals from
 * pushed-down quals.  This is convenient because for almost all purposes,
 * quals attached to a semijoin can be treated the same as innerjoin quals.
 */
#define IS_OUTER_JOIN(jointype) \
	(((1 << (jointype)) & \
	  ((1 << JOIN_LEFT) | \
	   (1 << JOIN_FULL) | \
	   (1 << JOIN_RIGHT) | \
	   (1 << JOIN_ANTI))) != 0)

/*
 * AggStrategy -
 *	  overall execution strategies for Agg plan nodes
 *
 * This is needed in both pathnodes.h and plannodes.h, so put it here...
 */
typedef enum AggStrategy
{
	AGG_PLAIN,					/* simple agg across all input rows */
	AGG_SORTED,					/* grouped agg, input must be sorted */
	AGG_HASHED,					/* grouped agg, use internal hashtable */
	AGG_MIXED					/* grouped agg, hash and sort both used */
} AggStrategy;

/*
 * AggSplit -
 *	  splitting (partial aggregation) modes for Agg plan nodes
 *
 * This is needed in both pathnodes.h and plannodes.h, so put it here...
 */

/* Primitive options supported by nodeAgg.c: */
#define AGGSPLITOP_COMBINE		0x01	/* substitute combinefn for transfn */
#define AGGSPLITOP_SKIPFINAL	0x02	/* skip finalfn, return state as-is */
#define AGGSPLITOP_SERIALIZE	0x04	/* apply serialfn to output */
#define AGGSPLITOP_DESERIALIZE	0x08	/* apply deserialfn to input */

/* Supported operating modes (i.e., useful combinations of these options): */
typedef enum AggSplit
{
	/* Basic, non-split aggregation: */
	AGGSPLIT_SIMPLE = 0,
	/* Initial phase of partial aggregation, with serialization: */
	AGGSPLIT_INITIAL_SERIAL = AGGSPLITOP_SKIPFINAL | AGGSPLITOP_SERIALIZE,
	/* Final phase of partial aggregation, with deserialization: */
	AGGSPLIT_FINAL_DESERIAL = AGGSPLITOP_COMBINE | AGGSPLITOP_DESERIALIZE
} AggSplit;

/* Test whether an AggSplit value selects each primitive option: */
#define DO_AGGSPLIT_COMBINE(as)		(((as) & AGGSPLITOP_COMBINE) != 0)
#define DO_AGGSPLIT_SKIPFINAL(as)	(((as) & AGGSPLITOP_SKIPFINAL) != 0)
#define DO_AGGSPLIT_SERIALIZE(as)	(((as) & AGGSPLITOP_SERIALIZE) != 0)
#define DO_AGGSPLIT_DESERIALIZE(as) (((as) & AGGSPLITOP_DESERIALIZE) != 0)

/*
 * SetOpCmd and SetOpStrategy -
 *	  overall semantics and execution strategies for SetOp plan nodes
 *
 * This is needed in both pathnodes.h and plannodes.h, so put it here...
 */
typedef enum SetOpCmd
{
	SETOPCMD_INTERSECT,
	SETOPCMD_INTERSECT_ALL,
	SETOPCMD_EXCEPT,
	SETOPCMD_EXCEPT_ALL
} SetOpCmd;

typedef enum SetOpStrategy
{
	SETOP_SORTED,				/* input must be sorted */
	SETOP_HASHED				/* use internal hashtable */
} SetOpStrategy;

/*
 * OnConflictAction -
 *	  "ON CONFLICT" clause type of query
 *
 * This is needed in both parsenodes.h and plannodes.h, so put it here...
 */
typedef enum OnConflictAction
{
	ONCONFLICT_NONE,			/* No "ON CONFLICT" clause */
	ONCONFLICT_NOTHING,			/* ON CONFLICT ... DO NOTHING */
	ONCONFLICT_UPDATE			/* ON CONFLICT ... DO UPDATE */
} OnConflictAction;

/*
 * LimitOption -
 *	LIMIT option of query
 *
 * This is needed in both parsenodes.h and plannodes.h, so put it here...
 */
typedef enum LimitOption
{
	LIMIT_OPTION_COUNT,			/* FETCH FIRST... ONLY */
	LIMIT_OPTION_WITH_TIES,		/* FETCH FIRST... WITH TIES */
	LIMIT_OPTION_DEFAULT,		/* No limit present */
} LimitOption;

#endif							/* NODES_H */