primnodes.h

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/*-------------------------------------------------------------------------
 *
 * primnodes.h
 *	  Definitions for "primitive" node types, those that are used in more
 *	  than one of the parse/plan/execute stages of the query pipeline.
 *	  Currently, these are mostly nodes for executable expressions
 *	  and join trees.
 *
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $Id: primnodes.h,v 1.92 2003/08/17 23:43:26 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef PRIMNODES_H
#define PRIMNODES_H

#include "access/attnum.h"
#include "nodes/pg_list.h"


/* ----------------------------------------------------------------
 *						node definitions
 * ----------------------------------------------------------------
 */

/*--------------------
 * Resdom (Result Domain)
 *
 * Notes:
 *
 * In a SELECT's targetlist, resno should always be equal to the item's
 * ordinal position (counting from 1).  However, in an INSERT or UPDATE
 * targetlist, resno represents the attribute number of the destination
 * column for the item; so there may be missing or out-of-order resnos.
 * In an UPDATE, it is even legal to have duplicated resnos; consider
 *		UPDATE table SET arraycol[1] = ..., arraycol[2] = ..., ...
 * The two meanings come together in the executor, because the planner
 * transforms INSERT/UPDATE tlists into a normalized form with exactly
 * one entry for each column of the destination table.  Before that's
 * happened, however, it is risky to assume that resno == position.
 * Generally get_tle_by_resno() should be used rather than nth() to fetch
 * tlist entries by resno.
 *
 * resname is required to represent the correct column name in non-resjunk
 * entries of top-level SELECT targetlists, since it will be used as the
 * column title sent to the frontend.  In most other contexts it is only
 * a debugging aid, and may be wrong or even NULL.  (In particular, it may
 * be wrong in a tlist from a stored rule, if the referenced column has been
 * renamed by ALTER TABLE since the rule was made.  Also, the planner tends
 * to store NULL rather than look up a valid name for tlist entries in
 * non-toplevel plan nodes.)  In resjunk entries, resname should be either
 * a specific system-generated name (such as "ctid") or NULL; anything else
 * risks confusing ExecGetJunkAttribute!
 *
 * ressortgroupref is used in the representation of ORDER BY and
 * GROUP BY items.	Targetlist entries with ressortgroupref=0 are not
 * sort/group items.  If ressortgroupref>0, then this item is an ORDER BY or
 * GROUP BY value.	No two entries in a targetlist may have the same nonzero
 * ressortgroupref --- but there is no particular meaning to the nonzero
 * values, except as tags.	(For example, one must not assume that lower
 * ressortgroupref means a more significant sort key.)	The order of the
 * associated SortClause or GroupClause lists determine the semantics.
 *
 * resorigtbl/resorigcol identify the source of the column, if it is a
 * simple reference to a column of a base table (or view).	If it is not
 * a simple reference, these fields are zeroes.
 *
 * If resjunk is true then the column is a working column (such as a sort key)
 * that should be removed from the final output of the query.  Resjunk columns
 * must have resnos that cannot duplicate any regular column's resno.  Also
 * note that there are places that assume resjunk columns come after non-junk
 * columns.
 *--------------------
 */
typedef struct Resdom
{
	NodeTag		type;
	AttrNumber	resno;			/* attribute number (see notes above) */
	Oid			restype;		/* type of the value */
	int32		restypmod;		/* type-specific modifier of the value */
	char	   *resname;		/* name of the column (could be NULL) */
	Index		ressortgroupref;/* nonzero if referenced by a sort/group
								 * clause */
	Oid			resorigtbl;		/* OID of column's source table */
	AttrNumber	resorigcol;		/* column's number in source table */
	bool		resjunk;		/* set to true to eliminate the attribute
								 * from final target list */
} Resdom;


/*
 * Alias -
 *	  specifies an alias for a range variable; the alias might also
 *	  specify renaming of columns within the table.
 */
typedef struct Alias
{
	NodeTag		type;
	char	   *aliasname;		/* aliased rel name (never qualified) */
	List	   *colnames;		/* optional list of column aliases */
	/* Note: colnames is a list of Value nodes (always strings) */
} Alias;

typedef enum InhOption
{
	INH_NO,						/* Do NOT scan child tables */
	INH_YES,					/* DO scan child tables */
	INH_DEFAULT					/* Use current SQL_inheritance option */
} InhOption;

/*
 * RangeVar - range variable, used in FROM clauses
 *
 * Also used to represent table names in utility statements; there, the alias
 * field is not used, and inhOpt shows whether to apply the operation
 * recursively to child tables.  In some contexts it is also useful to carry
 * a TEMP table indication here.
 */
typedef struct RangeVar
{
	NodeTag		type;
	char	   *catalogname;	/* the catalog (database) name, or NULL */
	char	   *schemaname;		/* the schema name, or NULL */
	char	   *relname;		/* the relation/sequence name */
	InhOption	inhOpt;			/* expand rel by inheritance? recursively
								 * act on children? */
	bool		istemp;			/* is this a temp relation/sequence? */
	Alias	   *alias;			/* table alias & optional column aliases */
} RangeVar;


/* ----------------------------------------------------------------
 *					node types for executable expressions
 * ----------------------------------------------------------------
 */

/*
 * Expr - generic superclass for executable-expression nodes
 *
 * All node types that are used in executable expression trees should derive
 * from Expr (that is, have Expr as their first field).  Since Expr only
 * contains NodeTag, this is a formality, but it is an easy form of
 * documentation.  See also the ExprState node types in execnodes.h.
 */
typedef struct Expr
{
	NodeTag		type;
} Expr;

/*
 * Var - expression node representing a variable (ie, a table column)
 *
 * Note: during parsing/planning, varnoold/varoattno are always just copies
 * of varno/varattno.  At the tail end of planning, Var nodes appearing in
 * upper-level plan nodes are reassigned to point to the outputs of their
 * subplans; for example, in a join node varno becomes INNER or OUTER and
 * varattno becomes the index of the proper element of that subplan's target
 * list.  But varnoold/varoattno continue to hold the original values.
 * The code doesn't really need varnoold/varoattno, but they are very useful
 * for debugging and interpreting completed plans, so we keep them around.
 */
#define    INNER		65000
#define    OUTER		65001

#define    PRS2_OLD_VARNO			1
#define    PRS2_NEW_VARNO			2

typedef struct Var
{
	Expr		xpr;
	Index		varno;			/* index of this var's relation in the
								 * range table (could also be INNER or
								 * OUTER) */
	AttrNumber	varattno;		/* attribute number of this var, or zero
								 * for all */
	Oid			vartype;		/* pg_type tuple OID for the type of this
								 * var */
	int32		vartypmod;		/* pg_attribute typmod value */
	Index		varlevelsup;

	/*
	 * for subquery variables referencing outer relations; 0 in a normal
	 * var, >0 means N levels up
	 */
	Index		varnoold;		/* original value of varno, for debugging */
	AttrNumber	varoattno;		/* original value of varattno */
} Var;

/*
 * Const
 */
typedef struct Const
{
	Expr		xpr;
	Oid			consttype;		/* PG_TYPE OID of the constant's datatype */
	int			constlen;		/* typlen of the constant's datatype */
	Datum		constvalue;		/* the constant's value */
	bool		constisnull;	/* whether the constant is null (if true,
								 * constvalue is undefined) */
	bool		constbyval;		/* whether this datatype is passed by
								 * value. If true, then all the
								 * information is stored in the Datum. If
								 * false, then the Datum contains a
								 * pointer to the information. */
} Const;

/* ----------------
 * Param
 *		paramkind - specifies the kind of parameter. The possible values
 *		for this field are specified in "params.h", and they are:
 *
 *		PARAM_NAMED: The parameter has a name, i.e. something
 *				like `$.salary' or `$.foobar'.
 *				In this case field `paramname' must be a valid name.
 *
 *		PARAM_NUM:	 The parameter has only a numeric identifier,
 *				i.e. something like `$1', `$2' etc.
 *				The number is contained in the `paramid' field.
 *
 *		PARAM_EXEC:  The parameter is an internal executor parameter.
 *				It has a number contained in the `paramid' field.
 * ----------------
 */
typedef struct Param
{
	Expr		xpr;
	int			paramkind;		/* kind of parameter. See above */
	AttrNumber	paramid;		/* numeric ID for parameter ("$1") */
	char	   *paramname;		/* name for parameter ("$.foo") */
	Oid			paramtype;		/* PG_TYPE OID of parameter's datatype */
} Param;

/*
 * Aggref
 */
typedef struct Aggref
{
	Expr		xpr;
	Oid			aggfnoid;		/* pg_proc Oid of the aggregate */
	Oid			aggtype;		/* type Oid of result of the aggregate */
	Expr	   *target;			/* expression we are aggregating on */
	Index		agglevelsup;	/* > 0 if agg belongs to outer query */
	bool		aggstar;		/* TRUE if argument was really '*' */
	bool		aggdistinct;	/* TRUE if it's agg(DISTINCT ...) */
} Aggref;

/* ----------------
 *	ArrayRef: describes an array subscripting operation
 *
 * An ArrayRef can describe fetching a single element from an array,
 * fetching a subarray (array slice), storing a single element into
 * an array, or storing a slice.  The "store" cases work with an
 * initial array value and a source value that is inserted into the
 * appropriate part of the array; the result of the operation is an
 * entire new modified array value.
 *
 * If reflowerindexpr = NIL, then we are fetching or storing a single array
 * element at the subscripts given by refupperindexpr.	Otherwise we are
 * fetching or storing an array slice, that is a rectangular subarray
 * with lower and upper bounds given by the index expressions.
 * reflowerindexpr must be the same length as refupperindexpr when it
 * is not NIL.
 *
 * Note: refrestype is NOT the element type, but the array type,
 * when doing subarray fetch or either type of store.
 * ----------------
 */
typedef struct ArrayRef
{
	Expr		xpr;
	Oid			refrestype;		/* type of the result of the ArrayRef
								 * operation */
	Oid			refarraytype;	/* type of the array proper */
	Oid			refelemtype;	/* type of the array elements */
	List	   *refupperindexpr;/* expressions that evaluate to upper