primnodes.h

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

 * 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 rowtype
 * Datum.  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;

/* ----------------
 * FieldStore
 *
 * FieldStore represents the operation of modifying one field in a tuple
 * value, yielding a new tuple value (the input is not touched!).  Like
 * the assign case of ArrayRef, this is used to implement UPDATE of a
 * portion of a column.
 *
 * A single FieldStore can actually represent updates of several different
 * fields.	The parser only generates FieldStores with single-element lists,
 * but the planner will collapse multiple updates of the same base column
 * into one FieldStore.
 * ----------------
 */

typedef struct FieldStore
{
	Expr		xpr;
	Expr	   *arg;			/* input tuple value */
	List	   *newvals;		/* new value(s) for field(s) */
	List	   *fieldnums;		/* integer list of field attnums */
	Oid			resulttype;		/* type of result (same as type of arg) */
	/* Like RowExpr, we deliberately omit a typmod here */
} FieldStore;

/* ----------------
 * 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
{
	Expr		xpr;
	Expr	   *arg;			/* input expression */
	Oid			resulttype;		/* output type of coercion expression */
	int32		resulttypmod;	/* output typmod (usually -1) */
	CoercionForm relabelformat; /* how to display this node */
} RelabelType;

/* ----------------
 * ConvertRowtypeExpr
 *
 * ConvertRowtypeExpr represents a type coercion from one composite type
 * to another, where the source type is guaranteed to contain all the columns
 * needed for the destination type plus possibly others; the columns need not
 * be in the same positions, but are matched up by name.  This is primarily
 * used to convert a whole-row value of an inheritance child table into a
 * valid whole-row value of its parent table's rowtype.
 * ----------------
 */

typedef struct ConvertRowtypeExpr
{
	Expr		xpr;
	Expr	   *arg;			/* input expression */
	Oid			resulttype;		/* output type (always a composite type) */
	/* result typmod is not stored, but must be -1; see RowExpr comments */
	CoercionForm convertformat; /* how to display this node */
} ConvertRowtypeExpr;

/*----------
 * CaseExpr - a CASE expression
 *
 * We support two distinct forms of CASE expression:
 *		CASE WHEN boolexpr THEN expr [ WHEN boolexpr THEN expr ... ]
 *		CASE testexpr WHEN compexpr THEN expr [ WHEN compexpr THEN expr ... ]
 * These are distinguishable by the "arg" field being NULL in the first case
 * and the testexpr in the second case.
 *
 * In the raw grammar output for the second form, the condition expressions
 * of the WHEN clauses are just the comparison values.	Parse analysis
 * converts these to valid boolean expressions of the form
 *		CaseTestExpr '=' compexpr
 * where the CaseTestExpr node is a placeholder that emits the correct
 * value at runtime.  This structure is used so that the testexpr need be
 * evaluated only once.  Note that after parse analysis, the condition
 * expressions always yield boolean.
 *
 * Note: we can test whether a CaseExpr has been through parse analysis
 * yet by checking whether casetype is InvalidOid or not.
 *----------
 */
typedef struct CaseExpr
{
	Expr		xpr;
	Oid			casetype;		/* type of expression result */
	Expr	   *arg;			/* implicit equality comparison argument */
	List	   *args;			/* the arguments (list of WHEN clauses) */
	Expr	   *defresult;		/* the default result (ELSE clause) */
} CaseExpr;

/*
 * CaseWhen - one arm of a CASE expression
 */
typedef struct CaseWhen
{
	Expr		xpr;
	Expr	   *expr;			/* condition expression */
	Expr	   *result;			/* substitution result */
} CaseWhen;

/*
 * Placeholder node for the test value to be processed by a CASE expression.
 * This is effectively like a Param, but can be implemented more simply
 * since we need only one replacement value at a time.
 *
 * We also use this in nested UPDATE expressions.
 * See transformAssignmentIndirection().
 */
typedef struct CaseTestExpr
{
	Expr		xpr;
	Oid			typeId;			/* type for substituted value */
	int32		typeMod;		/* typemod for substituted value */
} CaseTestExpr;

/*
 * ArrayExpr - an ARRAY[] expression
 *
 * Note: if multidims is false, the constituent expressions all yield the
 * scalar type identified by element_typeid.  If multidims is true, the
 * constituent expressions all yield arrays of element_typeid (ie, the same
 * type as array_typeid); at runtime we must check for compatible subscripts.
 */
typedef struct ArrayExpr
{
	Expr		xpr;
	Oid			array_typeid;	/* type of expression result */
	Oid			element_typeid; /* common type of array elements */
	List	   *elements;		/* the array elements or sub-arrays */
	bool		multidims;		/* true if elements are sub-arrays */
} ArrayExpr;

/*
 * RowExpr - a ROW() expression
 *
 * Note: the list of fields must have a one-for-one correspondence with
 * physical fields of the associated rowtype, although it is okay for it
 * to be shorter than the rowtype.	That is, the N'th list element must
 * match up with the N'th physical field.  When the N'th physical field
 * is a dropped column (attisdropped) then the N'th list element can just
 * be a NULL constant.	(This case can only occur for named composite types,
 * not RECORD types, since those are built from the RowExpr itself rather