primnodes.h

来自「PostgreSQL7.4.6 for Linux」· C头文件 代码 · 共 832 行 · 第 1/3 页

								 * array indexes */
	List	   *reflowerindexpr;/* expressions that evaluate to lower
								 * array indexes */
	Expr	   *refexpr;		/* the expression that evaluates to an
								 * array value */
	Expr	   *refassgnexpr;	/* expression for the source value, or
								 * NULL if fetch */
} ArrayRef;

/*
 * CoercionContext - distinguishes the allowed set of type casts
 *
 * NB: ordering of the alternatives is significant; later (larger) values
 * allow more casts than earlier ones.
 */
typedef enum CoercionContext
{
	COERCION_IMPLICIT,			/* coercion in context of expression */
	COERCION_ASSIGNMENT,		/* coercion in context of assignment */
	COERCION_EXPLICIT			/* explicit cast operation */
} CoercionContext;

/*
 * CoercionForm - information showing how to display a function-call node
 */
typedef enum CoercionForm
{
	COERCE_EXPLICIT_CALL,		/* display as a function call */
	COERCE_EXPLICIT_CAST,		/* display as an explicit cast */
	COERCE_IMPLICIT_CAST,		/* implicit cast, so hide it */
	COERCE_DONTCARE				/* special case for pathkeys */
} CoercionForm;

/*
 * FuncExpr - expression node for a function call
 */
typedef struct FuncExpr
{
	Expr		xpr;
	Oid			funcid;			/* PG_PROC OID of the function */
	Oid			funcresulttype; /* PG_TYPE OID of result value */
	bool		funcretset;		/* true if function returns set */
	CoercionForm funcformat;	/* how to display this function call */
	List	   *args;			/* arguments to the function */
} FuncExpr;

/*
 * OpExpr - expression node for an operator invocation
 *
 * Semantically, this is essentially the same as a function call.
 *
 * Note that opfuncid is not necessarily filled in immediately on creation
 * of the node.  The planner makes sure it is valid before passing the node
 * tree to the executor, but during parsing/planning opfuncid is typically 0.
 */
typedef struct OpExpr
{
	Expr		xpr;
	Oid			opno;			/* PG_OPERATOR OID of the operator */
	Oid			opfuncid;		/* PG_PROC OID of underlying function */
	Oid			opresulttype;	/* PG_TYPE OID of result value */
	bool		opretset;		/* true if operator returns set */
	List	   *args;			/* arguments to the operator (1 or 2) */
} OpExpr;

/*
 * DistinctExpr - expression node for "x IS DISTINCT FROM y"
 *
 * Except for the nodetag, this is represented identically to an OpExpr
 * referencing the "=" operator for x and y.
 * We use "=", not the more obvious "<>", because more datatypes have "="
 * than "<>".  This means the executor must invert the operator result.
 * Note that the operator function won't be called at all if either input
 * is NULL, since then the result can be determined directly.
 */
typedef OpExpr DistinctExpr;

/*
 * ScalarArrayOpExpr - expression node for "scalar op ANY/ALL (array)"
 *
 * The operator must yield boolean.  It is applied to the left operand
 * and each element of the righthand array, and the results are combined
 * with OR or AND (for ANY or ALL respectively).  The node representation
 * is almost the same as for the underlying operator, but we need a useOr
 * flag to remember whether it's ANY or ALL, and we don't have to store
 * the result type because it must be boolean.
 */
typedef struct ScalarArrayOpExpr
{
	Expr		xpr;
	Oid			opno;			/* PG_OPERATOR OID of the operator */
	Oid			opfuncid;		/* PG_PROC OID of underlying function */
	bool		useOr;			/* true for ANY, false for ALL */
	List	   *args;			/* the scalar and array operands */
} ScalarArrayOpExpr;

/*
 * BoolExpr - expression node for the basic Boolean operators AND, OR, NOT
 *
 * Notice the arguments are given as a List.  For NOT, of course the list
 * must always have exactly one element.  For AND and OR, the executor can
 * handle any number of arguments.	The parser treats AND and OR as binary
 * and so it only produces two-element lists, but the optimizer will flatten
 * trees of AND and OR nodes to produce longer lists when possible.
 */
typedef enum BoolExprType
{
	AND_EXPR, OR_EXPR, NOT_EXPR
} BoolExprType;

typedef struct BoolExpr
{
	Expr		xpr;
	BoolExprType boolop;
	List	   *args;			/* arguments to this expression */
} BoolExpr;

/* ----------------
 * SubLink
 *
 * A SubLink represents a subselect appearing in an expression, and in some
 * cases also the combining operator(s) just above it.	The subLinkType
 * indicates the form of the expression represented:
 *	EXISTS_SUBLINK		EXISTS(SELECT ...)
 *	ALL_SUBLINK			(lefthand) op ALL (SELECT ...)
 *	ANY_SUBLINK			(lefthand) op ANY (SELECT ...)
 *	MULTIEXPR_SUBLINK	(lefthand) op (SELECT ...)
 *	EXPR_SUBLINK		(SELECT with single targetlist item ...)
 *	ARRAY_SUBLINK		ARRAY(SELECT with single targetlist item ...)
 * For ALL, ANY, and MULTIEXPR, the lefthand is a list of expressions of the
 * same length as the subselect's targetlist.  MULTIEXPR will *always* have
 * a list with more than one entry; if the subselect has just one target
 * then the parser will create an EXPR_SUBLINK instead (and any operator
 * above the subselect will be represented separately).  Note that both
 * MULTIEXPR and EXPR require the subselect to deliver only one row.
 * ARRAY requires just one target column, and creates an array of the target
 * column's type using one or more rows resulting from the subselect.
 * ALL, ANY, and MULTIEXPR require the combining operators to deliver boolean
 * results.  These are reduced to one result per row using OR or AND semantics
 * depending on the "useOr" flag.  ALL and ANY combine the per-row results
 * using AND and OR semantics respectively.
 *
 * SubLink is classed as an Expr node, but it is not actually executable;
 * it must be replaced in the expression tree by a SubPlan node during
 * planning.
 *
 * NOTE: in the raw output of gram.y, lefthand contains a list of raw
 * expressions; useOr and operOids are not filled in yet.  Also, subselect
 * is a raw parsetree.	During parse analysis, the parser transforms the
 * lefthand expression list using normal expression transformation rules.
 * It fills operOids with the OIDs representing the specific operator(s)
 * to apply to each pair of lefthand and targetlist expressions.
 * And subselect is transformed to a Query.  This is the representation
 * seen in saved rules and in the rewriter.
 *
 * In EXISTS, EXPR, and ARRAY SubLinks, lefthand, operName, and operOids are
 * unused and are always NIL.  useOr is not significant either for these
 * sublink types.
 * ----------------
 */
typedef enum SubLinkType
{
	EXISTS_SUBLINK,
	ALL_SUBLINK,
	ANY_SUBLINK,
	MULTIEXPR_SUBLINK,
	EXPR_SUBLINK,
	ARRAY_SUBLINK
} SubLinkType;


typedef struct SubLink
{
	Expr		xpr;
	SubLinkType subLinkType;	/* EXISTS, ALL, ANY, MULTIEXPR, EXPR */
	bool		useOr;			/* TRUE to combine column results with
								 * "OR" not "AND" */
	List	   *lefthand;		/* list of outer-query expressions on the
								 * left */
	List	   *operName;		/* originally specified operator name */
	List	   *operOids;		/* OIDs of actual combining operators */
	Node	   *subselect;		/* subselect as Query* or parsetree */
} SubLink;

/*
 * SubPlan - executable expression node for a subplan (sub-SELECT)
 *
 * The planner replaces SubLink nodes in expression trees with SubPlan
 * nodes after it has finished planning the subquery.  SubPlan contains
 * a sub-plantree and rtable instead of a sub-Query.
 *
 * In an ordinary subplan, "exprs" points to a list of executable expressions
 * (OpExpr trees) for the combining operators; their left-hand arguments are
 * the original lefthand expressions, and their right-hand arguments are
 * PARAM_EXEC Param nodes representing the outputs of the sub-select.
 * (NOTE: runtime coercion functions may be inserted as well.)	But if the
 * sub-select becomes an initplan rather than a subplan, these executable
 * expressions are part of the outer plan's expression tree (and the SubPlan
 * node itself is not).  In this case "exprs" is NIL to avoid duplication.
 *
 * The planner also derives lists of the values that need to be passed into
 * and out of the subplan.	Input values are represented as a list "args" of
 * expressions to be evaluated in the outer-query context (currently these
 * args are always just Vars, but in principle they could be any expression).
 * The values are assigned to the global PARAM_EXEC params indexed by parParam
 * (the parParam and args lists must have the same ordering).  setParam is a
 * list of the PARAM_EXEC params that are computed by the sub-select, if it
 * is an initplan; they are listed in order by sub-select output column
 * position.  (parParam and setParam are integer Lists, not Bitmapsets,
 * because their ordering is significant.)
 */
typedef struct SubPlan
{
	Expr		xpr;
	/* Fields copied from original SubLink: */
	SubLinkType subLinkType;	/* EXISTS, ALL, ANY, MULTIEXPR, EXPR */
	bool		useOr;			/* TRUE to combine column results with
								 * "OR" not "AND" */
	/* The combining operators, transformed to executable expressions: */
	List	   *exprs;			/* list of OpExpr expression trees */
	List	   *paramIds;		/* IDs of Params embedded in the above */
	/* Note: paramIds has a one-to-one correspondence to the exprs list */
	/* The subselect, transformed to a Plan: */
	struct Plan *plan;			/* subselect plan itself */
	int			plan_id;		/* dummy thing because of we haven't equal
								 * funcs for plan nodes... actually, we
								 * could put *plan itself somewhere else
								 * (TopPlan node ?)... */
	List	   *rtable;			/* range table for subselect */
	/* Information about execution strategy: */
	bool		useHashTable;	/* TRUE to store subselect output in a
								 * hash table (implies we are doing "IN") */
	bool		unknownEqFalse; /* TRUE if it's okay to return FALSE when
								 * the spec result is UNKNOWN; this allows
								 * much simpler handling of null values */
	/* Information for passing params into and out of the subselect: */
	/* setParam and parParam are lists of integers (param IDs) */
	List	   *setParam;		/* initplan subqueries have to set these
								 * Params for parent plan */
	List	   *parParam;		/* indices of input Params from parent
								 * plan */
	List	   *args;			/* exprs to pass as parParam values */
} SubPlan;

/* ----------------
 * FieldSelect
 *
 * FieldSelect represents the operation of extracting one field from a tuple
 * value.  At runtime, the input expression is expected to yield a Datum
 * that contains a pointer-to-TupleTableSlot.  The specified field number
 * is extracted and returned as a Datum.
 * ----------------
 */

typedef struct FieldSelect
{
	Expr		xpr;
	Expr	   *arg;			/* input expression */
	AttrNumber	fieldnum;		/* attribute number of field to extract */
	Oid			resulttype;		/* type of the field (result type of this
								 * node) */
	int32		resulttypmod;	/* output typmod (usually -1) */
} FieldSelect;

/* ----------------
 * RelabelType
 *
 * RelabelType represents a "dummy" type coercion between two binary-
 * compatible datatypes, such as reinterpreting the result of an OID
 * expression as an int4.  It is a no-op at runtime; we only need it
 * to provide a place to store the correct type to be attributed to
 * the expression result during type resolution.  (We can't get away
 * with just overwriting the type field of the input expression node,
 * so we need a separate node to show the coercion's result type.)
 * ----------------
 */

typedef struct RelabelType