parsenodes.h

/*-------------------------------------------------------------------------
 *
 * parsenodes.h
 *	  definitions for parse tree nodes
 *
 * Many of the node types used in parsetrees include a "location" field.
 * This is a byte (not character) offset in the original source text, to be
 * used for positioning an error cursor when there is an error related to
 * the node.  Access to the original source text is needed to make use of
 * the location.
 *
 *
 * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/nodes/parsenodes.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PARSENODES_H
#define PARSENODES_H

#include "nodes/bitmapset.h"
#include "nodes/primnodes.h"
#include "nodes/value.h"

/* Possible sources of a Query */
typedef enum QuerySource
{
	QSRC_ORIGINAL,				/* original parsetree (explicit query) */
	QSRC_PARSER,				/* added by parse analysis (now unused) */
	QSRC_INSTEAD_RULE,			/* added by unconditional INSTEAD rule */
	QSRC_QUAL_INSTEAD_RULE,		/* added by conditional INSTEAD rule */
	QSRC_NON_INSTEAD_RULE		/* added by non-INSTEAD rule */
} QuerySource;

/* Sort ordering options for ORDER BY and CREATE INDEX */
typedef enum SortByDir
{
	SORTBY_DEFAULT,
	SORTBY_ASC,
	SORTBY_DESC,
	SORTBY_USING				/* not allowed in CREATE INDEX ... */
} SortByDir;

typedef enum SortByNulls
{
	SORTBY_NULLS_DEFAULT,
	SORTBY_NULLS_FIRST,
	SORTBY_NULLS_LAST
} SortByNulls;

/*
 * Grantable rights are encoded so that we can OR them together in a bitmask.
 * The present representation of AclItem limits us to 16 distinct rights,
 * even though AclMode is defined as uint32.  See utils/acl.h.
 *
 * Caution: changing these codes breaks stored ACLs, hence forces initdb.
 */
typedef uint32 AclMode;			/* a bitmask of privilege bits */

#define ACL_INSERT		(1<<0)	/* for relations */
#define ACL_SELECT		(1<<1)
#define ACL_UPDATE		(1<<2)
#define ACL_DELETE		(1<<3)
#define ACL_TRUNCATE	(1<<4)
#define ACL_REFERENCES	(1<<5)
#define ACL_TRIGGER		(1<<6)
#define ACL_EXECUTE		(1<<7)	/* for functions */
#define ACL_USAGE		(1<<8)	/* for languages, namespaces, FDWs, and
								 * servers */
#define ACL_CREATE		(1<<9)	/* for namespaces and databases */
#define ACL_CREATE_TEMP (1<<10) /* for databases */
#define ACL_CONNECT		(1<<11) /* for databases */
#define N_ACL_RIGHTS	12		/* 1 plus the last 1<<x */
#define ACL_NO_RIGHTS	0
/* Currently, SELECT ... FOR UPDATE/FOR SHARE requires UPDATE privileges */
#define ACL_SELECT_FOR_UPDATE	ACL_UPDATE


/*****************************************************************************
 *	Query Tree
 *****************************************************************************/

/*
 * Query -
 *	  Parse analysis turns all statements into a Query tree (via transformStmt)
 *	  for further processing by the rewriter and planner.
 *
 *	  Utility statements (i.e. non-optimizable statements) have the
 *	  utilityStmt field set, and the Query itself is mostly dummy.
 *	  DECLARE CURSOR is a special case: it is represented like a SELECT,
 *	  but the original DeclareCursorStmt is stored in utilityStmt.
 *
 *	  Planning converts a Query tree into a Plan tree headed by a PlannedStmt
 *	  node --- the Query structure is not used by the executor.
 */
typedef struct Query
{
	NodeTag		type;

	CmdType		commandType;	/* select|insert|update|delete|utility */

	QuerySource querySource;	/* where did I come from? */

	bool		canSetTag;		/* do I set the command result tag? */

	Node	   *utilityStmt;	/* non-null if this is DECLARE CURSOR or a
								 * non-optimizable statement */

	int			resultRelation; /* rtable index of target relation for
								 * INSERT/UPDATE/DELETE; 0 for SELECT */

	IntoClause *intoClause;		/* target for SELECT INTO / CREATE TABLE AS */

	bool		hasAggs;		/* has aggregates in tlist or havingQual */
	bool		hasWindowFuncs; /* has window functions in tlist */
	bool		hasSubLinks;	/* has subquery SubLink */
	bool		hasDistinctOn;	/* distinctClause is from DISTINCT ON */
	bool		hasRecursive;	/* WITH RECURSIVE was specified */
	bool		hasModifyingCTE;	/* has INSERT/UPDATE/DELETE in WITH */
	bool		hasForUpdate;	/* FOR UPDATE or FOR SHARE was specified */

	List	   *cteList;		/* WITH list (of CommonTableExpr's) */

	List	   *rtable;			/* list of range table entries */
	FromExpr   *jointree;		/* table join tree (FROM and WHERE clauses) */

	List	   *targetList;		/* target list (of TargetEntry) */

	List	   *returningList;	/* return-values list (of TargetEntry) */

	List	   *groupClause;	/* a list of SortGroupClause's */

	Node	   *havingQual;		/* qualifications applied to groups */

	List	   *windowClause;	/* a list of WindowClause's */

	List	   *distinctClause; /* a list of SortGroupClause's */

	List	   *sortClause;		/* a list of SortGroupClause's */

	Node	   *limitOffset;	/* # of result tuples to skip (int8 expr) */
	Node	   *limitCount;		/* # of result tuples to return (int8 expr) */

	List	   *rowMarks;		/* a list of RowMarkClause's */

	Node	   *setOperations;	/* set-operation tree if this is top level of
								 * a UNION/INTERSECT/EXCEPT query */

	List	   *constraintDeps; /* a list of pg_constraint OIDs that the query
								 * depends on to be semantically valid */
} Query;


/****************************************************************************
 *	Supporting data structures for Parse Trees
 *
 *	Most of these node types appear in raw parsetrees output by the grammar,
 *	and get transformed to something else by the analyzer.	A few of them
 *	are used as-is in transformed querytrees.
 ****************************************************************************/

/*
 * TypeName - specifies a type in definitions
 *
 * For TypeName structures generated internally, it is often easier to
 * specify the type by OID than by name.  If "names" is NIL then the
 * actual type OID is given by typeOid, otherwise typeOid is unused.
 * Similarly, if "typmods" is NIL then the actual typmod is expected to
 * be prespecified in typemod, otherwise typemod is unused.
 *
 * If pct_type is TRUE, then names is actually a field name and we look up
 * the type of that field.	Otherwise (the normal case), names is a type
 * name possibly qualified with schema and database name.
 */
typedef struct TypeName
{
	NodeTag		type;
	List	   *names;			/* qualified name (list of Value strings) */
	Oid			typeOid;		/* type identified by OID */
	bool		setof;			/* is a set? */
	bool		pct_type;		/* %TYPE specified? */
	List	   *typmods;		/* type modifier expression(s) */
	int32		typemod;		/* prespecified type modifier */
	List	   *arrayBounds;	/* array bounds */
	int			location;		/* token location, or -1 if unknown */
} TypeName;

/*
 * ColumnRef - specifies a reference to a column, or possibly a whole tuple
 *
 * The "fields" list must be nonempty.	It can contain string Value nodes
 * (representing names) and A_Star nodes (representing occurrence of a '*').
 * Currently, A_Star must appear only as the last list element --- the grammar
 * is responsible for enforcing this!
 *
 * Note: any array subscripting or selection of fields from composite columns
 * is represented by an A_Indirection node above the ColumnRef.  However,
 * for simplicity in the normal case, initial field selection from a table
 * name is represented within ColumnRef and not by adding A_Indirection.
 */
typedef struct ColumnRef
{
	NodeTag		type;
	List	   *fields;			/* field names (Value strings) or A_Star */
	int			location;		/* token location, or -1 if unknown */
} ColumnRef;

/*
 * ParamRef - specifies a $n parameter reference
 */
typedef struct ParamRef
{
	NodeTag		type;
	int			number;			/* the number of the parameter */
	int			location;		/* token location, or -1 if unknown */
} ParamRef;

/*
 * A_Expr - infix, prefix, and postfix expressions
 */
typedef enum A_Expr_Kind
{
	AEXPR_OP,					/* normal operator */
	AEXPR_AND,					/* booleans - name field is unused */
	AEXPR_OR,
	AEXPR_NOT,
	AEXPR_OP_ANY,				/* scalar op ANY (array) */
	AEXPR_OP_ALL,				/* scalar op ALL (array) */
	AEXPR_DISTINCT,				/* IS DISTINCT FROM - name must be "=" */
	AEXPR_NULLIF,				/* NULLIF - name must be "=" */
	AEXPR_OF,					/* IS [NOT] OF - name must be "=" or "<>" */
	AEXPR_IN					/* [NOT] IN - name must be "=" or "<>" */
} A_Expr_Kind;

typedef struct A_Expr
{
	NodeTag		type;
	A_Expr_Kind kind;			/* see above */
	List	   *name;			/* possibly-qualified name of operator */
	Node	   *lexpr;			/* left argument, or NULL if none */
	Node	   *rexpr;			/* right argument, or NULL if none */
	int			location;		/* token location, or -1 if unknown */
} A_Expr;

/*
 * A_Const - a literal constant
 */
typedef struct A_Const
{
	NodeTag		type;
	Value		val;			/* value (includes type info, see value.h) */
	int			location;		/* token location, or -1 if unknown */
} A_Const;

/*
 * TypeCast - a CAST expression
 */
typedef struct TypeCast
{
	NodeTag		type;
	Node	   *arg;			/* the expression being casted */
	TypeName   *typeName;		/* the target type */
	int			location;		/* token location, or -1 if unknown */
} TypeCast;

/*
 * CollateClause - a COLLATE expression
 */
typedef struct CollateClause
{
	NodeTag		type;
	Node	   *arg;			/* input expression */
	List	   *collname;		/* possibly-qualified collation name */
	int			location;		/* token location, or -1 if unknown */
} CollateClause;

/*
 * FuncCall - a function or aggregate invocation
 *
 * agg_order (if not NIL) indicates we saw 'foo(... ORDER BY ...)'.
 * agg_star indicates we saw a 'foo(*)' construct, while agg_distinct
 * indicates we saw 'foo(DISTINCT ...)'.  In any of these cases, the
 * construct *must* be an aggregate call.  Otherwise, it might be either an
 * aggregate or some other kind of function.  However, if OVER is present
 * it had better be an aggregate or window function.
 */
typedef struct FuncCall
{
	NodeTag		type;
	List	   *funcname;		/* qualified name of function */
	List	   *args;			/* the arguments (list of exprs) */
	List	   *agg_order;		/* ORDER BY (list of SortBy) */
	bool		agg_star;		/* argument was really '*' */
	bool		agg_distinct;	/* arguments were labeled DISTINCT */
	bool		func_variadic;	/* last argument was labeled VARIADIC */
	struct WindowDef *over;		/* OVER clause, if any */
	int			location;		/* token location, or -1 if unknown */
} FuncCall;

/*
 * A_Star - '*' representing all columns of a table or compound field
 *
 * This can appear within ColumnRef.fields, A_Indirection.indirection, and
 * ResTarget.indirection lists.
 */
typedef struct A_Star
{
	NodeTag		type;
} A_Star;

/*
 * A_Indices - array subscript or slice bounds ([lidx:uidx] or [uidx])
 */
typedef struct A_Indices
{
	NodeTag		type;
	Node	   *lidx;			/* NULL if it's a single subscript */
	Node	   *uidx;
} A_Indices;

/*
 * A_Indirection - select a field and/or array element from an expression
 *
 * The indirection list can contain A_Indices nodes (representing
 * subscripting), string Value nodes (representing field selection --- the
 * string value is the name of the field to select), and A_Star nodes
 * (representing selection of all fields of a composite type).
 * For example, a complex selection operation like
 *				(foo).field1[42][7].field2
 * would be represented with a single A_Indirection node having a 4-element
 * indirection list.
 *
 * Currently, A_Star must appear only as the last list element --- the grammar
 * is responsible for enforcing this!
 */
typedef struct A_Indirection
{
	NodeTag		type;
	Node	   *arg;			/* the thing being selected from */
	List	   *indirection;	/* subscripts and/or field names and/or * */
} A_Indirection;

/*
 * A_ArrayExpr - an ARRAY[] construct
 */
typedef struct A_ArrayExpr
{
	NodeTag		type;
	List	   *elements;		/* array element expressions */
	int			location;		/* token location, or -1 if unknown */
} A_ArrayExpr;

/*
 * ResTarget -
 *	  result target (used in target list of pre-transformed parse trees)
 *
 * In a SELECT target list, 'name' is the column label from an
 * 'AS ColumnLabel' clause, or NULL if there was none, and 'val' is the
 * value expression itself.  The 'indirection' field is not used.
 *
 * INSERT uses ResTarget in its target-column-names list.  Here, 'name' is
 * the name of the destination column, 'indirection' stores any subscripts
 * attached to the destination, and 'val' is not used.
 *
 * In an UPDATE target list, 'name' is the name of the destination column,
 * 'indirection' stores any subscripts attached to the destination, and
 * 'val' is the expression to assign.
 *
 * See A_Indirection for more info about what can appear in 'indirection'.
 */
typedef struct ResTarget
{
	NodeTag		type;
	char	   *name;			/* column name or NULL */
	List	   *indirection;	/* subscripts, field names, and '*', or NIL */
	Node	   *val;			/* the value expression to compute or assign */
	int			location;		/* token location, or -1 if unknown */
} ResTarget;

/*
 * SortBy - for ORDER BY clause
 */
typedef struct SortBy
{
	NodeTag		type;
	Node	   *node;			/* expression to sort on */
	SortByDir	sortby_dir;		/* ASC/DESC/USING/default */
	SortByNulls sortby_nulls;	/* NULLS FIRST/LAST */
	List	   *useOp;			/* name of op to use, if SORTBY_USING */
	int			location;		/* operator location, or -1 if none/unknown */
} SortBy;

/*
 * WindowDef - raw representation of WINDOW and OVER clauses
 *
 * For entries in a WINDOW list, "name" is the window name being defined.
 * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
 * for the "OVER (window)" syntax, which is subtly different --- the latter
 * implies overriding the window frame clause.
 */
typedef struct WindowDef
{
	NodeTag		type;
	char	   *name;			/* window's own name */
	char	   *refname;		/* referenced window name, if any */
	List	   *partitionClause;	/* PARTITION BY expression list */
	List	   *orderClause;	/* ORDER BY (list of SortBy) */
	int			frameOptions;	/* frame_clause options, see below */
	Node	   *startOffset;	/* expression for starting bound, if any */
	Node	   *endOffset;		/* expression for ending bound, if any */
	int			location;		/* parse location, or -1 if none/unknown */
} WindowDef;

/*
 * frameOptions is an OR of these bits.  The NONDEFAULT and BETWEEN bits are
 * used so that ruleutils.c can tell which properties were specified and
 * which were defaulted; the correct behavioral bits must be set either way.
 * The START_foo and END_foo options must come in pairs of adjacent bits for
 * the convenience of gram.y, even though some of them are useless/invalid.
 * We will need more bits (and fields) to cover the full SQL:2008 option set.
 */
#define FRAMEOPTION_NONDEFAULT					0x00001 /* any specified? */
#define FRAMEOPTION_RANGE						0x00002 /* RANGE behavior */
#define FRAMEOPTION_ROWS						0x00004 /* ROWS behavior */
#define FRAMEOPTION_BETWEEN						0x00008 /* BETWEEN given? */
#define FRAMEOPTION_START_UNBOUNDED_PRECEDING	0x00010 /* start is U. P. */
#define FRAMEOPTION_END_UNBOUNDED_PRECEDING		0x00020 /* (disallowed) */
#define FRAMEOPTION_START_UNBOUNDED_FOLLOWING	0x00040 /* (disallowed) */
#define FRAMEOPTION_END_UNBOUNDED_FOLLOWING		0x00080 /* end is U. F. */
#define FRAMEOPTION_START_CURRENT_ROW			0x00100 /* start is C. R. */
#define FRAMEOPTION_END_CURRENT_ROW				0x00200 /* end is C. R. */
#define FRAMEOPTION_START_VALUE_PRECEDING		0x00400 /* start is V. P. */
#define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
#define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
#define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */

#define FRAMEOPTION_START_VALUE \
	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
#define FRAMEOPTION_END_VALUE \
	(FRAMEOPTION_END_VALUE_PRECEDING | FRAMEOPTION_END_VALUE_FOLLOWING)

#define FRAMEOPTION_DEFAULTS \
	(FRAMEOPTION_RANGE | FRAMEOPTION_START_UNBOUNDED_PRECEDING | \
	 FRAMEOPTION_END_CURRENT_ROW)

/*
 * RangeSubselect - subquery appearing in a FROM clause
 */
typedef struct RangeSubselect
{
	NodeTag		type;
	Node	   *subquery;		/* the untransformed sub-select clause */
	Alias	   *alias;			/* table alias & optional column aliases */
} RangeSubselect;

/*
 * RangeFunction - function call appearing in a FROM clause
 */
typedef struct RangeFunction
{
	NodeTag		type;
	Node	   *funccallnode;	/* untransformed function call tree */
	Alias	   *alias;			/* table alias & optional column aliases */
	List	   *coldeflist;		/* list of ColumnDef nodes to describe result
								 * of function returning RECORD */
} RangeFunction;

/*
 * ColumnDef - column definition (used in various creates)
 *
 * If the column has a default value, we may have the value expression
 * in either "raw" form (an untransformed parse tree) or "cooked" form
 * (a post-parse-analysis, executable expression tree), depending on
 * how this ColumnDef node was created (by parsing, or by inheritance
 * from an existing relation).	We should never have both in the same node!
 *
 * Similarly, we may have a COLLATE specification in either raw form
 * (represented as a CollateClause with arg==NULL) or cooked form
 * (the collation's OID).
 *
 * The constraints list may contain a CONSTR_DEFAULT item in a raw
 * parsetree produced by gram.y, but transformCreateStmt will remove
 * the item and set raw_default instead.  CONSTR_DEFAULT items
 * should not appear in any subsequent processing.
 */
typedef struct ColumnDef
{
	NodeTag		type;
	char	   *colname;		/* name of column */
	TypeName   *typeName;		/* type of column */
	int			inhcount;		/* number of times column is inherited */
	bool		is_local;		/* column has local (non-inherited) def'n */
	bool		is_not_null;	/* NOT NULL constraint specified? */
	bool		is_from_type;	/* column definition came from table type */
	char		storage;		/* attstorage setting, or 0 for default */
	Node	   *raw_default;	/* default value (untransformed parse tree) */
	Node	   *cooked_default; /* default value (transformed expr tree) */
	CollateClause *collClause;	/* untransformed COLLATE spec, if any */
	Oid			collOid;		/* collation OID (InvalidOid if not set) */
	List	   *constraints;	/* other constraints on column */
	List	   *fdwoptions;		/* per-column FDW options */
} ColumnDef;

/*
 * inhRelation - Relation a CREATE TABLE is to inherit attributes of
 */
typedef struct InhRelation
{
	NodeTag		type;
	RangeVar   *relation;
	bits32		options;		/* OR of CreateStmtLikeOption flags */
} InhRelation;

typedef enum CreateStmtLikeOption
{
	CREATE_TABLE_LIKE_DEFAULTS = 1 << 0,
	CREATE_TABLE_LIKE_CONSTRAINTS = 1 << 1,
	CREATE_TABLE_LIKE_INDEXES = 1 << 2,
	CREATE_TABLE_LIKE_STORAGE = 1 << 3,
	CREATE_TABLE_LIKE_COMMENTS = 1 << 4,
	CREATE_TABLE_LIKE_ALL = 0x7FFFFFFF
} CreateStmtLikeOption;

/*
 * IndexElem - index parameters (used in CREATE INDEX)
 *
 * For a plain index attribute, 'name' is the name of the table column to
 * index, and 'expr' is NULL.  For an index expression, 'name' is NULL and
 * 'expr' is the expression tree.
 */
typedef struct IndexElem
{
	NodeTag		type;
	char	   *name;			/* name of attribute to index, or NULL */
	Node	   *expr;			/* expression to index, or NULL */
	char	   *indexcolname;	/* name for index column; NULL = default */
	List	   *collation;		/* name of collation; NIL = default */
	List	   *opclass;		/* name of desired opclass; NIL = default */
	SortByDir	ordering;		/* ASC/DESC/default */
	SortByNulls nulls_ordering; /* FIRST/LAST/default */
} IndexElem;

/*
 * DefElem - a generic "name = value" option definition
 *
 * In some contexts the name can be qualified.	Also, certain SQL commands
 * allow a SET/ADD/DROP action to be attached to option settings, so it's
 * convenient to carry a field for that too.  (Note: currently, it is our
 * practice that the grammar allows namespace and action only in statements
 * where they are relevant; C code can just ignore those fields in other
 * statements.)
 */
typedef enum DefElemAction
{
	DEFELEM_UNSPEC,				/* no action given */
	DEFELEM_SET,
	DEFELEM_ADD,
	DEFELEM_DROP
} DefElemAction;

typedef struct DefElem
{
	NodeTag		type;
	char	   *defnamespace;	/* NULL if unqualified name */
	char	   *defname;
	Node	   *arg;			/* a (Value *) or a (TypeName *) */
	DefElemAction defaction;	/* unspecified action, or SET/ADD/DROP */
} DefElem;

/*
 * LockingClause - raw representation of FOR UPDATE/SHARE options
 *
 * Note: lockedRels == NIL means "all relations in query".	Otherwise it
 * is a list of RangeVar nodes.  (We use RangeVar mainly because it carries
 * a location field --- currently, parse analysis insists on unqualified
 * names in LockingClause.)
 */
typedef struct LockingClause
{
	NodeTag		type;
	List	   *lockedRels;		/* FOR UPDATE or FOR SHARE relations */
	bool		forUpdate;		/* true = FOR UPDATE, false = FOR SHARE */
	bool		noWait;			/* NOWAIT option */
} LockingClause;

/*
 * XMLSERIALIZE (in raw parse tree only)
 */
typedef struct XmlSerialize
{
	NodeTag		type;
	XmlOptionType xmloption;	/* DOCUMENT or CONTENT */
	Node	   *expr;
	TypeName   *typeName;
	int			location;		/* token location, or -1 if unknown */
} XmlSerialize;


/****************************************************************************
 *	Nodes for a Query tree
 ****************************************************************************/

/*--------------------
 * RangeTblEntry -
 *	  A range table is a List of RangeTblEntry nodes.
 *
 *	  A range table entry may represent a plain relation, a sub-select in
 *	  FROM, or the result of a JOIN clause.  (Only explicit JOIN syntax
 *	  produces an RTE, not the implicit join resulting from multiple FROM
 *	  items.  This is because we only need the RTE to deal with SQL features
 *	  like outer joins and join-output-column aliasing.)  Other special
 *	  RTE types also exist, as indicated by RTEKind.
 *
 *	  Note that we consider RTE_RELATION to cover anything that has a pg_class
 *	  entry.  relkind distinguishes the sub-cases.
 *
 *	  alias is an Alias node representing the AS alias-clause attached to the
 *	  FROM expression, or NULL if no clause.
 *
 *	  eref is the table reference name and column reference names (either
 *	  real or aliases).  Note that system columns (OID etc) are not included
 *	  in the column list.
 *	  eref->aliasname is required to be present, and should generally be used
 *	  to identify the RTE for error messages etc.
 *
 *	  In RELATION RTEs, the colnames in both alias and eref are indexed by
 *	  physical attribute number; this means there must be colname entries for
 *	  dropped columns.	When building an RTE we insert empty strings ("") for
 *	  dropped columns.	Note however that a stored rule may have nonempty
 *	  colnames for columns dropped since the rule was created (and for that
 *	  matter the colnames might be out of date due to column renamings).
 *	  The same comments apply to FUNCTION RTEs when the function's return type
 *	  is a named composite type.
 *
 *	  In JOIN RTEs, the colnames in both alias and eref are one-to-one with
 *	  joinaliasvars entries.  A JOIN RTE will omit columns of its inputs when
 *	  those columns are known to be dropped at parse time.	Again, however,
 *	  a stored rule might contain entries for columns dropped since the rule
 *	  was created.	(This is only possible for columns not actually referenced
 *	  in the rule.)  When loading a stored rule, we replace the joinaliasvars
 *	  items for any such columns with NULL Consts.	(We can't simply delete
 *	  them from the joinaliasvars list, because that would affect the attnums
 *	  of Vars referencing the rest of the list.)
 *
 *	  inh is TRUE for relation references that should be expanded to include
 *	  inheritance children, if the rel has any.  This *must* be FALSE for
 *	  RTEs other than RTE_RELATION entries.
 *
 *	  inFromCl marks those range variables that are listed in the FROM clause.
 *	  It's false for RTEs that are added to a query behind the scenes, such
 *	  as the NEW and OLD variables for a rule, or the subqueries of a UNION.
 *	  This flag is not used anymore during parsing, since the parser now uses
 *	  a separate "namespace" data structure to control visibility, but it is
 *	  needed by ruleutils.c to determine whether RTEs should be shown in
 *	  decompiled queries.
 *
 *	  requiredPerms and checkAsUser specify run-time access permissions
 *	  checks to be performed at query startup.	The user must have *all*
 *	  of the permissions that are OR'd together in requiredPerms (zero
 *	  indicates no permissions checking).  If checkAsUser is not zero,
 *	  then do the permissions checks using the access rights of that user,
 *	  not the current effective user ID.  (This allows rules to act as
 *	  setuid gateways.)  Permissions checks only apply to RELATION RTEs.
 *
 *	  For SELECT/INSERT/UPDATE permissions, if the user doesn't have
 *	  table-wide permissions then it is sufficient to have the permissions
 *	  on all columns identified in selectedCols (for SELECT) and/or
 *	  modifiedCols (for INSERT/UPDATE; we can tell which from the query type).
 *	  selectedCols and modifiedCols are bitmapsets, which cannot have negative
 *	  integer members, so we subtract FirstLowInvalidHeapAttributeNumber from
 *	  column numbers before storing them in these fields.  A whole-row Var
 *	  reference is represented by setting the bit for InvalidAttrNumber.
 *--------------------
 */
typedef enum RTEKind
{
	RTE_RELATION,				/* ordinary relation reference */
	RTE_SUBQUERY,				/* subquery in FROM */
	RTE_JOIN,					/* join */
	RTE_FUNCTION,				/* function in FROM */
	RTE_VALUES,					/* VALUES (<exprlist>), (<exprlist>), ... */
	RTE_CTE						/* common table expr (WITH list element) */
} RTEKind;

typedef struct RangeTblEntry
{
	NodeTag		type;

	RTEKind		rtekind;		/* see above */

	/*
	 * XXX the fields applicable to only some rte kinds should be merged into
	 * a union.  I didn't do this yet because the diffs would impact a lot of
	 * code that is being actively worked on.  FIXME someday.
	 */

	/*
	 * Fields valid for a plain relation RTE (else zero):
	 */
	Oid			relid;			/* OID of the relation */
	char		relkind;		/* relation kind (see pg_class.relkind) */

	/*
	 * Fields valid for a subquery RTE (else NULL):
	 */
	Query	   *subquery;		/* the sub-query */

	/*
	 * Fields valid for a join RTE (else NULL/zero):
	 *
	 * joinaliasvars is a list of Vars or COALESCE expressions corresponding
	 * to the columns of the join result.  An alias Var referencing column K
	 * of the join result can be replaced by the K'th element of joinaliasvars
	 * --- but to simplify the task of reverse-listing aliases correctly, we
	 * do not do that until planning time.	In a Query loaded from a stored
	 * rule, it is also possible for joinaliasvars items to be NULL Consts,
	 * denoting columns dropped since the rule was made.
	 */
	JoinType	jointype;		/* type of join */
	List	   *joinaliasvars;	/* list of alias-var expansions */

	/*
	 * Fields valid for a function RTE (else NULL):
	 *
	 * If the function returns RECORD, funccoltypes lists the column types
	 * declared in the RTE's column type specification, funccoltypmods lists
	 * their declared typmods, funccolcollations their collations.	Otherwise,
	 * those fields are NIL.
	 */
	Node	   *funcexpr;		/* expression tree for func call */
	List	   *funccoltypes;	/* OID list of column type OIDs */
	List	   *funccoltypmods; /* integer list of column typmods */
	List	   *funccolcollations;		/* OID list of column collation OIDs */

	/*
	 * Fields valid for a values RTE (else NIL):
	 */
	List	   *values_lists;	/* list of expression lists */
	List	   *values_collations;		/* OID list of column collation OIDs */

	/*
	 * Fields valid for a CTE RTE (else NULL/zero):
	 */
	char	   *ctename;		/* name of the WITH list item */
	Index		ctelevelsup;	/* number of query levels up */
	bool		self_reference; /* is this a recursive self-reference? */
	List	   *ctecoltypes;	/* OID list of column type OIDs */
	List	   *ctecoltypmods;	/* integer list of column typmods */
	List	   *ctecolcollations;		/* OID list of column collation OIDs */

	/*
	 * Fields valid in all RTEs:
	 */
	Alias	   *alias;			/* user-written alias clause, if any */
	Alias	   *eref;			/* expanded reference names */
	bool		inh;			/* inheritance requested? */
	bool		inFromCl;		/* present in FROM clause? */
	AclMode		requiredPerms;	/* bitmask of required access permissions */
	Oid			checkAsUser;	/* if valid, check access as this role */
	Bitmapset  *selectedCols;	/* columns needing SELECT permission */
	Bitmapset  *modifiedCols;	/* columns needing INSERT/UPDATE permission */
} RangeTblEntry;

/*
 * SortGroupClause -
 *		representation of ORDER BY, GROUP BY, PARTITION BY,
 *		DISTINCT, DISTINCT ON items
 *
 * You might think that ORDER BY is only interested in defining ordering,
 * and GROUP/DISTINCT are only interested in defining equality.  However,
 * one way to implement grouping is to sort and then apply a "uniq"-like
 * filter.	So it's also interesting to keep track of possible sort operators
 * for GROUP/DISTINCT, and in particular to try to sort for the grouping
 * in a way that will also yield a requested ORDER BY ordering.  So we need
 * to be able to compare ORDER BY and GROUP/DISTINCT lists, which motivates
 * the decision to give them the same representation.
 *
 * tleSortGroupRef must match ressortgroupref of exactly one entry of the
 *		query's targetlist; that is the expression to be sorted or grouped by.
 * eqop is the OID of the equality operator.
 * sortop is the OID of the ordering operator (a "<" or ">" operator),
 *		or InvalidOid if not available.
 * nulls_first means about what you'd expect.  If sortop is InvalidOid
 *		then nulls_first is meaningless and should be set to false.
 * hashable is TRUE if eqop is hashable (note this condition also depends
 *		on the datatype of the input expression).
 *
 * In an ORDER BY item, all fields must be valid.  (The eqop isn't essential
 * here, but it's cheap to get it along with the sortop, and requiring it
 * to be valid eases comparisons to grouping items.)  Note that this isn't
 * actually enough information to determine an ordering: if the sortop is
 * collation-sensitive, a collation OID is needed too.	We don't store the
 * collation in SortGroupClause because it's not available at the time the
 * parser builds the SortGroupClause; instead, consult the exposed collation
 * of the referenced targetlist expression to find out what it is.
 *
 * In a grouping item, eqop must be valid.	If the eqop is a btree equality
 * operator, then sortop should be set to a compatible ordering operator.
 * We prefer to set eqop/sortop/nulls_first to match any ORDER BY item that
 * the query presents for the same tlist item.	If there is none, we just
 * use the default ordering op for the datatype.
 *
 * If the tlist item's type has a hash opclass but no btree opclass, then
 * we will set eqop to the hash equality operator, sortop to InvalidOid,
 * and nulls_first to false.  A grouping item of this kind can only be
 * implemented by hashing, and of course it'll never match an ORDER BY item.
 *
 * The hashable flag is provided since we generally have the requisite
 * information readily available when the SortGroupClause is constructed,
 * and it's relatively expensive to get it again later.  Note there is no
 * need for a "sortable" flag since OidIsValid(sortop) serves the purpose.
 *
 * A query might have both ORDER BY and DISTINCT (or DISTINCT ON) clauses.
 * In SELECT DISTINCT, the distinctClause list is as long or longer than the
 * sortClause list, while in SELECT DISTINCT ON it's typically shorter.
 * The two lists must match up to the end of the shorter one --- the parser
 * rearranges the distinctClause if necessary to make this true.  (This
 * restriction ensures that only one sort step is needed to both satisfy the
 * ORDER BY and set up for the Unique step.  This is semantically necessary
 * for DISTINCT ON, and presents no real drawback for DISTINCT.)
 */
typedef struct SortGroupClause
{
	NodeTag		type;
	Index		tleSortGroupRef;	/* reference into targetlist */
	Oid			eqop;			/* the equality operator ('=' op) */
	Oid			sortop;			/* the ordering operator ('<' op), or 0 */
	bool		nulls_first;	/* do NULLs come before normal values? */
	bool		hashable;		/* can eqop be implemented by hashing? */
} SortGroupClause;

/*
 * WindowClause -
 *		transformed representation of WINDOW and OVER clauses
 *
 * A parsed Query's windowClause list contains these structs.  "name" is set
 * if the clause originally came from WINDOW, and is NULL if it originally
 * was an OVER clause (but note that we collapse out duplicate OVERs).
 * partitionClause and orderClause are lists of SortGroupClause structs.
 * winref is an ID number referenced by WindowFunc nodes; it must be unique
 * among the members of a Query's windowClause list.
 * When refname isn't null, the partitionClause is always copied from there;
 * the orderClause might or might not be copied (see copiedOrder); the framing
 * options are never copied, per spec.
 */
typedef struct WindowClause
{
	NodeTag		type;
	char	   *name;			/* window name (NULL in an OVER clause) */
	char	   *refname;		/* referenced window name, if any */
	List	   *partitionClause;	/* PARTITION BY list */
	List	   *orderClause;	/* ORDER BY list */
	int			frameOptions;	/* frame_clause options, see WindowDef */
	Node	   *startOffset;	/* expression for starting bound, if any */
	Node	   *endOffset;		/* expression for ending bound, if any */
	Index		winref;			/* ID referenced by window functions */
	bool		copiedOrder;	/* did we copy orderClause from refname? */
} WindowClause;

/*
 * RowMarkClause -
 *	   parser output representation of FOR UPDATE/SHARE clauses
 *
 * Query.rowMarks contains a separate RowMarkClause node for each relation
 * identified as a FOR UPDATE/SHARE target.  If FOR UPDATE/SHARE is applied
 * to a subquery, we generate RowMarkClauses for all normal and subquery rels
 * in the subquery, but they are marked pushedDown = true to distinguish them
 * from clauses that were explicitly written at this query level.  Also,
 * Query.hasForUpdate tells whether there were explicit FOR UPDATE/SHARE
 * clauses in the current query level.
 */
typedef struct RowMarkClause
{
	NodeTag		type;
	Index		rti;			/* range table index of target relation */
	bool		forUpdate;		/* true = FOR UPDATE, false = FOR SHARE */
	bool		noWait;			/* NOWAIT option */
	bool		pushedDown;		/* pushed down from higher query level? */
} RowMarkClause;

/*
 * WithClause -
 *	   representation of WITH clause
 *
 * Note: WithClause does not propagate into the Query representation;
 * but CommonTableExpr does.
 */
typedef struct WithClause
{
	NodeTag		type;
	List	   *ctes;			/* list of CommonTableExprs */
	bool		recursive;		/* true = WITH RECURSIVE */
	int			location;		/* token location, or -1 if unknown */
} WithClause;

/*
 * CommonTableExpr -
 *	   representation of WITH list element
 *
 * We don't currently support the SEARCH or CYCLE clause.
 */
typedef struct CommonTableExpr
{
	NodeTag		type;
	char	   *ctename;		/* query name (never qualified) */
	List	   *aliascolnames;	/* optional list of column names */
	/* SelectStmt/InsertStmt/etc before parse analysis, Query afterwards: */
	Node	   *ctequery;		/* the CTE's subquery */
	int			location;		/* token location, or -1 if unknown */
	/* These fields are set during parse analysis: */
	bool		cterecursive;	/* is this CTE actually recursive? */
	int			cterefcount;	/* number of RTEs referencing this CTE
								 * (excluding internal self-references) */
	List	   *ctecolnames;	/* list of output column names */
	List	   *ctecoltypes;	/* OID list of output column type OIDs */
	List	   *ctecoltypmods;	/* integer list of output column typmods */
	List	   *ctecolcollations;		/* OID list of column collation OIDs */
} CommonTableExpr;

/* Convenience macro to get the output tlist of a CTE's query */
#define GetCTETargetList(cte) \
	(AssertMacro(IsA((cte)->ctequery, Query)), \
	 ((Query *) (cte)->ctequery)->commandType == CMD_SELECT ? \
	 ((Query *) (cte)->ctequery)->targetList : \
	 ((Query *) (cte)->ctequery)->returningList)


/*****************************************************************************
 *		Optimizable Statements
 *****************************************************************************/

/* ----------------------
 *		Insert Statement
 *
 * The source expression is represented by SelectStmt for both the
 * SELECT and VALUES cases.  If selectStmt is NULL, then the query
 * is INSERT ... DEFAULT VALUES.
 * ----------------------
 */
typedef struct InsertStmt
{
	NodeTag		type;
	RangeVar   *relation;		/* relation to insert into */
	List	   *cols;			/* optional: names of the target columns */
	Node	   *selectStmt;		/* the source SELECT/VALUES, or NULL */
	List	   *returningList;	/* list of expressions to return */
	WithClause *withClause;		/* WITH clause */
} InsertStmt;

/* ----------------------
 *		Delete Statement
 * ----------------------
 */
typedef struct DeleteStmt
{
	NodeTag		type;
	RangeVar   *relation;		/* relation to delete from */
	List	   *usingClause;	/* optional using clause for more tables */
	Node	   *whereClause;	/* qualifications */
	List	   *returningList;	/* list of expressions to return */
	WithClause *withClause;		/* WITH clause */
} DeleteStmt;

/* ----------------------
 *		Update Statement
 * ----------------------
 */
typedef struct UpdateStmt
{
	NodeTag		type;
	RangeVar   *relation;		/* relation to update */
	List	   *targetList;		/* the target list (of ResTarget) */
	Node	   *whereClause;	/* qualifications */
	List	   *fromClause;		/* optional from clause for more tables */
	List	   *returningList;	/* list of expressions to return */
	WithClause *withClause;		/* WITH clause */
} UpdateStmt;

/* ----------------------
 *		Select Statement
 *
 * A "simple" SELECT is represented in the output of gram.y by a single
 * SelectStmt node; so is a VALUES construct.  A query containing set
 * operators (UNION, INTERSECT, EXCEPT) is represented by a tree of SelectStmt
 * nodes, in which the leaf nodes are component SELECTs and the internal nodes
 * represent UNION, INTERSECT, or EXCEPT operators.  Using the same node
 * type for both leaf and internal nodes allows gram.y to stick ORDER BY,
 * LIMIT, etc, clause values into a SELECT statement without worrying
 * whether it is a simple or compound SELECT.
 * ----------------------
 */
typedef enum SetOperation
{
	SETOP_NONE = 0,
	SETOP_UNION,
	SETOP_INTERSECT,
	SETOP_EXCEPT
} SetOperation;