dependency.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 1,809 行 · 第 1/4 页

/*-------------------------------------------------------------------------
 *
 * dependency.c
 *	  Routines to support inter-object dependencies.
 *
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.31 2003/08/11 23:04:49 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "catalog/catname.h"
#include "catalog/dependency.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_cast.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_conversion.h"
#include "catalog/pg_depend.h"
#include "catalog/pg_language.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_trigger.h"
#include "commands/comment.h"
#include "commands/defrem.h"
#include "commands/proclang.h"
#include "commands/schemacmds.h"
#include "commands/trigger.h"
#include "commands/typecmds.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "optimizer/clauses.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteRemove.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


/* This enum covers all system catalogs whose OIDs can appear in classid. */
typedef enum ObjectClasses
{
	OCLASS_CLASS,				/* pg_class */
	OCLASS_PROC,				/* pg_proc */
	OCLASS_TYPE,				/* pg_type */
	OCLASS_CAST,				/* pg_cast */
	OCLASS_CONSTRAINT,			/* pg_constraint */
	OCLASS_CONVERSION,			/* pg_conversion */
	OCLASS_DEFAULT,				/* pg_attrdef */
	OCLASS_LANGUAGE,			/* pg_language */
	OCLASS_OPERATOR,			/* pg_operator */
	OCLASS_OPCLASS,				/* pg_opclass */
	OCLASS_REWRITE,				/* pg_rewrite */
	OCLASS_TRIGGER,				/* pg_trigger */
	OCLASS_SCHEMA,				/* pg_namespace */
	MAX_OCLASS					/* MUST BE LAST */
} ObjectClasses;

/* expansible list of ObjectAddresses */
typedef struct
{
	ObjectAddress *refs;		/* => palloc'd array */
	int			numrefs;		/* current number of references */
	int			maxrefs;		/* current size of palloc'd array */
} ObjectAddresses;

/* for find_expr_references_walker */
typedef struct
{
	ObjectAddresses addrs;		/* addresses being accumulated */
	List	   *rtables;		/* list of rangetables to resolve Vars */
} find_expr_references_context;


/*
 * Because not all system catalogs have predetermined OIDs, we build a table
 * mapping between ObjectClasses and OIDs.	This is done at most once per
 * backend run, to minimize lookup overhead.
 */
static bool object_classes_initialized = false;
static Oid	object_classes[MAX_OCLASS];


static void findAutoDeletableObjects(const ObjectAddress *object,
						 ObjectAddresses *oktodelete,
						 Relation depRel);
static bool recursiveDeletion(const ObjectAddress *object,
				  DropBehavior behavior,
				  int msglevel,
				  const ObjectAddress *callingObject,
				  ObjectAddresses *oktodelete,
				  Relation depRel);
static bool deleteDependentObjects(const ObjectAddress *object,
					   const char *objDescription,
					   DropBehavior behavior,
					   int msglevel,
					   ObjectAddresses *oktodelete,
					   Relation depRel);
static void doDeletion(const ObjectAddress *object);
static bool find_expr_references_walker(Node *node,
							find_expr_references_context *context);
static void eliminate_duplicate_dependencies(ObjectAddresses *addrs);
static int	object_address_comparator(const void *a, const void *b);
static void init_object_addresses(ObjectAddresses *addrs);
static void add_object_address(ObjectClasses oclass, Oid objectId, int32 subId,
				   ObjectAddresses *addrs);
static void add_exact_object_address(const ObjectAddress *object,
						 ObjectAddresses *addrs);
static bool object_address_present(const ObjectAddress *object,
					   ObjectAddresses *addrs);
static void term_object_addresses(ObjectAddresses *addrs);
static void init_object_classes(void);
static ObjectClasses getObjectClass(const ObjectAddress *object);
static char *getObjectDescription(const ObjectAddress *object);
static void getRelationDescription(StringInfo buffer, Oid relid);


/*
 * performDeletion: attempt to drop the specified object.  If CASCADE
 * behavior is specified, also drop any dependent objects (recursively).
 * If RESTRICT behavior is specified, error out if there are any dependent
 * objects, except for those that should be implicitly dropped anyway
 * according to the dependency type.
 *
 * This is the outer control routine for all forms of DROP that drop objects
 * that can participate in dependencies.
 */
void
performDeletion(const ObjectAddress *object,
				DropBehavior behavior)
{
	char	   *objDescription;
	Relation	depRel;
	ObjectAddresses oktodelete;

	/*
	 * Get object description for possible use in failure message. Must do
	 * this before deleting it ...
	 */
	objDescription = getObjectDescription(object);

	/*
	 * We save some cycles by opening pg_depend just once and passing the
	 * Relation pointer down to all the recursive deletion steps.
	 */
	depRel = heap_openr(DependRelationName, RowExclusiveLock);

	/*
	 * Construct a list of objects that are reachable by AUTO or INTERNAL
	 * dependencies from the target object.  These should be deleted
	 * silently, even if the actual deletion pass first reaches one of
	 * them via a non-auto dependency.
	 */
	init_object_addresses(&oktodelete);

	findAutoDeletableObjects(object, &oktodelete, depRel);

	if (!recursiveDeletion(object, behavior, NOTICE,
						   NULL, &oktodelete, depRel))
		ereport(ERROR,
				(errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
			  errmsg("cannot drop %s because other objects depend on it",
					 objDescription),
				 errhint("Use DROP ... CASCADE to drop the dependent objects too.")));

	term_object_addresses(&oktodelete);

	heap_close(depRel, RowExclusiveLock);

	pfree(objDescription);
}


/*
 * deleteWhatDependsOn: attempt to drop everything that depends on the
 * specified object, though not the object itself.	Behavior is always
 * CASCADE.
 *
 * This is currently used only to clean out the contents of a schema
 * (namespace): the passed object is a namespace.  We normally want this
 * to be done silently, so there's an option to suppress NOTICE messages.
 */
void
deleteWhatDependsOn(const ObjectAddress *object,
					bool showNotices)
{
	char	   *objDescription;
	Relation	depRel;
	ObjectAddresses oktodelete;

	/*
	 * Get object description for possible use in failure messages
	 */
	objDescription = getObjectDescription(object);

	/*
	 * We save some cycles by opening pg_depend just once and passing the
	 * Relation pointer down to all the recursive deletion steps.
	 */
	depRel = heap_openr(DependRelationName, RowExclusiveLock);

	/*
	 * Construct a list of objects that are reachable by AUTO or INTERNAL
	 * dependencies from the target object.  These should be deleted
	 * silently, even if the actual deletion pass first reaches one of
	 * them via a non-auto dependency.
	 */
	init_object_addresses(&oktodelete);

	findAutoDeletableObjects(object, &oktodelete, depRel);

	/*
	 * Now invoke only step 2 of recursiveDeletion: just recurse to the
	 * stuff dependent on the given object.
	 */
	if (!deleteDependentObjects(object, objDescription,
								DROP_CASCADE,
								showNotices ? NOTICE : DEBUG2,
								&oktodelete, depRel))
		ereport(ERROR,
				(errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
				 errmsg("failed to drop all objects depending on %s",
						objDescription)));

	/*
	 * We do not need CommandCounterIncrement here, since if step 2 did
	 * anything then each recursive call will have ended with one.
	 */

	term_object_addresses(&oktodelete);

	heap_close(depRel, RowExclusiveLock);

	pfree(objDescription);
}


/*
 * findAutoDeletableObjects: find all objects that are reachable by AUTO or
 * INTERNAL dependency paths from the given object.  Add them all to the
 * oktodelete list.  Note that the originally given object will also be
 * added to the list.
 *
 * depRel is the already-open pg_depend relation.
 */
static void
findAutoDeletableObjects(const ObjectAddress *object,
						 ObjectAddresses *oktodelete,
						 Relation depRel)
{
	ScanKeyData key[3];
	int			nkeys;
	SysScanDesc scan;
	HeapTuple	tup;
	ObjectAddress otherObject;

	/*
	 * If this object is already in oktodelete, then we already visited
	 * it; don't do so again (this prevents infinite recursion if there's
	 * a loop in pg_depend).  Otherwise, add it.
	 */
	if (object_address_present(object, oktodelete))
		return;
	add_exact_object_address(object, oktodelete);

	/*
	 * Scan pg_depend records that link to this object, showing the things
	 * that depend on it.  For each one that is AUTO or INTERNAL, visit
	 * the referencing object.
	 *
	 * When dropping a whole object (subId = 0), find pg_depend records for
	 * its sub-objects too.
	 */
	ScanKeyEntryInitialize(&key[0], 0x0,
						   Anum_pg_depend_refclassid, F_OIDEQ,
						   ObjectIdGetDatum(object->classId));
	ScanKeyEntryInitialize(&key[1], 0x0,
						   Anum_pg_depend_refobjid, F_OIDEQ,
						   ObjectIdGetDatum(object->objectId));
	if (object->objectSubId != 0)
	{
		ScanKeyEntryInitialize(&key[2], 0x0,
							   Anum_pg_depend_refobjsubid, F_INT4EQ,
							   Int32GetDatum(object->objectSubId));
		nkeys = 3;
	}
	else
		nkeys = 2;

	scan = systable_beginscan(depRel, DependReferenceIndex, true,
							  SnapshotNow, nkeys, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		Form_pg_depend foundDep = (Form_pg_depend) GETSTRUCT(tup);

		switch (foundDep->deptype)
		{
			case DEPENDENCY_NORMAL:
				/* ignore */
				break;
			case DEPENDENCY_AUTO:
			case DEPENDENCY_INTERNAL:
				/* recurse */
				otherObject.classId = foundDep->classid;
				otherObject.objectId = foundDep->objid;
				otherObject.objectSubId = foundDep->objsubid;
				findAutoDeletableObjects(&otherObject, oktodelete, depRel);
				break;
			case DEPENDENCY_PIN:

				/*
				 * For a PIN dependency we just ereport immediately; there
				 * won't be any others to examine, and we aren't ever
				 * going to let the user delete it.
				 */
				ereport(ERROR,
						(errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
						 errmsg("cannot drop %s because it is required by the database system",
								getObjectDescription(object))));
				break;
			default:
				elog(ERROR, "unrecognized dependency type '%c' for %s",
					 foundDep->deptype, getObjectDescription(object));
				break;
		}
	}

	systable_endscan(scan);
}


/*
 * recursiveDeletion: delete a single object for performDeletion, plus
 * (recursively) anything that depends on it.
 *
 * Returns TRUE if successful, FALSE if not.
 *
 * callingObject is NULL at the outer level, else identifies the object that
 * we recursed from (the reference object that someone else needs to delete).
 *
 * oktodelete is a list of objects verified deletable (ie, reachable by one
 * or more AUTO or INTERNAL dependencies from the original target).
 *
 * depRel is the already-open pg_depend relation.
 *
 *
 * In RESTRICT mode, we perform all the deletions anyway, but ereport a message
 * and return FALSE if we find a restriction violation.  performDeletion
 * will then abort the transaction to nullify the deletions.  We have to
 * do it this way to (a) report all the direct and indirect dependencies
 * while (b) not going into infinite recursion if there's a cycle.
 *
 * This is even more complex than one could wish, because it is possible for
 * the same pair of objects to be related by both NORMAL and AUTO/INTERNAL
 * dependencies.  Also, we might have a situation where we've been asked to
 * delete object A, and objects B and C both have AUTO dependencies on A,
 * but B also has a NORMAL dependency on C.  (Since any of these paths might
 * be indirect, we can't prevent these scenarios, but must cope instead.)
 * If we visit C before B then we would mistakenly decide that the B->C link
 * should prevent the restricted drop from occurring.  To handle this, we make
 * a pre-scan to find all the objects that are auto-deletable from A.  If we
 * visit C first, but B is present in the oktodelete list, then we make no
 * complaint but recurse to delete B anyway.  (Note that in general we must
 * delete B before deleting C; the drop routine for B may try to access C.)
 *
 * Note: in the case where the path to B is traversed first, we will not
 * see the NORMAL dependency when we reach C, because of the pg_depend
 * removals done in step 1.  The oktodelete list is necessary just
 * to make the behavior independent of the order in which pg_depend
 * entries are visited.
 */
static bool
recursiveDeletion(const ObjectAddress *object,
				  DropBehavior behavior,
				  int msglevel,
				  const ObjectAddress *callingObject,
				  ObjectAddresses *oktodelete,
				  Relation depRel)
{
	bool		ok = true;
	char	   *objDescription;
	ScanKeyData key[3];
	int			nkeys;
	SysScanDesc scan;
	HeapTuple	tup;
	ObjectAddress otherObject;
	ObjectAddress owningObject;
	bool		amOwned = false;

	/*
	 * Get object description for possible use in messages.  Must do this
	 * before deleting it ...
	 */
	objDescription = getObjectDescription(object);

	/*
	 * Step 1: find and remove pg_depend records that link from this
	 * object to others.  We have to do this anyway, and doing it first
	 * ensures that we avoid infinite recursion in the case of cycles.
	 * Also, some dependency types require extra processing here.
	 *
	 * When dropping a whole object (subId = 0), remove all pg_depend records
	 * for its sub-objects too.
	 */
	ScanKeyEntryInitialize(&key[0], 0x0,
						   Anum_pg_depend_classid, F_OIDEQ,
						   ObjectIdGetDatum(object->classId));
	ScanKeyEntryInitialize(&key[1], 0x0,
						   Anum_pg_depend_objid, F_OIDEQ,
						   ObjectIdGetDatum(object->objectId));
	if (object->objectSubId != 0)
	{
		ScanKeyEntryInitialize(&key[2], 0x0,
							   Anum_pg_depend_objsubid, F_INT4EQ,
							   Int32GetDatum(object->objectSubId));
		nkeys = 3;
	}
	else
		nkeys = 2;

	scan = systable_beginscan(depRel, DependDependerIndex, true,
							  SnapshotNow, nkeys, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		Form_pg_depend foundDep = (Form_pg_depend) GETSTRUCT(tup);

		otherObject.classId = foundDep->refclassid;
		otherObject.objectId = foundDep->refobjid;
		otherObject.objectSubId = foundDep->refobjsubid;

		switch (foundDep->deptype)
		{
			case DEPENDENCY_NORMAL:
			case DEPENDENCY_AUTO:
				/* no problem */
				break;
			case DEPENDENCY_INTERNAL:

				/*
				 * This object is part of the internal implementation of