pg_shdepend.c

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/*-------------------------------------------------------------------------
 *
 * pg_shdepend.c
 *    routines to support manipulation of the pg_shdepend relation
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/catalog/pg_shdepend.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_conversion.h"
#include "catalog/pg_database.h"
#include "catalog/pg_default_acl.h"
#include "catalog/pg_event_trigger.h"
#include "catalog/pg_extension.h"
#include "catalog/pg_foreign_data_wrapper.h"
#include "catalog/pg_foreign_server.h"
#include "catalog/pg_language.h"
#include "catalog/pg_largeobject.h"
#include "catalog/pg_largeobject_metadata.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_opfamily.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_shdepend.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_type.h"
#include "commands/alter.h"
#include "commands/dbcommands.h"
#include "commands/collationcmds.h"
#include "commands/conversioncmds.h"
#include "commands/defrem.h"
#include "commands/event_trigger.h"
#include "commands/extension.h"
#include "commands/proclang.h"
#include "commands/schemacmds.h"
#include "commands/tablecmds.h"
#include "commands/typecmds.h"
#include "storage/lmgr.h"
#include "miscadmin.h"
#include "utils/acl.h"
#include "utils/fmgroids.h"
#include "utils/syscache.h"
#include "utils/tqual.h"


typedef enum
{
    LOCAL_OBJECT,
    SHARED_OBJECT,
    REMOTE_OBJECT
} objectType;

static void getOidListDiff(Oid *list1, int *nlist1, Oid *list2, int *nlist2);
static Oid  classIdGetDbId(Oid classId);
static void shdepChangeDep(Relation sdepRel,
               Oid classid, Oid objid, int32 objsubid,
               Oid refclassid, Oid refobjid,
               SharedDependencyType deptype);
static void shdepAddDependency(Relation sdepRel,
                   Oid classId, Oid objectId, int32 objsubId,
                   Oid refclassId, Oid refobjId,
                   SharedDependencyType deptype);
static void shdepDropDependency(Relation sdepRel,
                    Oid classId, Oid objectId, int32 objsubId,
                    bool drop_subobjects,
                    Oid refclassId, Oid refobjId,
                    SharedDependencyType deptype);
static void storeObjectDescription(StringInfo descs, objectType type,
                       ObjectAddress *object,
                       SharedDependencyType deptype,
                       int count);
static bool isSharedObjectPinned(Oid classId, Oid objectId, Relation sdepRel);


/*
 * recordSharedDependencyOn
 *
 * Record a dependency between 2 objects via their respective ObjectAddresses.
 * The first argument is the dependent object, the second the one it
 * references (which must be a shared object).
 *
 * This locks the referenced object and makes sure it still exists.
 * Then it creates an entry in pg_shdepend.  The lock is kept until
 * the end of the transaction.
 *
 * Dependencies on pinned objects are not recorded.
 */
void
recordSharedDependencyOn(ObjectAddress *depender,
                         ObjectAddress *referenced,
                         SharedDependencyType deptype)
{
    Relation    sdepRel;

    /*
     * Objects in pg_shdepend can't have SubIds.
     */
    Assert(depender->objectSubId == 0);
    Assert(referenced->objectSubId == 0);

    /*
     * During bootstrap, do nothing since pg_shdepend may not exist yet.
     * initdb will fill in appropriate pg_shdepend entries after bootstrap.
     */
    if (IsBootstrapProcessingMode())
        return;

    sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

    /* If the referenced object is pinned, do nothing. */
    if (!isSharedObjectPinned(referenced->classId, referenced->objectId,
                              sdepRel))
    {
        shdepAddDependency(sdepRel, depender->classId, depender->objectId,
                           depender->objectSubId,
                           referenced->classId, referenced->objectId,
                           deptype);
    }

    heap_close(sdepRel, RowExclusiveLock);
}

/*
 * recordDependencyOnOwner
 *
 * A convenient wrapper of recordSharedDependencyOn -- register the specified
 * user as owner of the given object.
 *
 * Note: it's the caller's responsibility to ensure that there isn't an owner
 * entry for the object already.
 */
void
recordDependencyOnOwner(Oid classId, Oid objectId, Oid owner)
{
    ObjectAddress myself,
                referenced;

    myself.classId = classId;
    myself.objectId = objectId;
    myself.objectSubId = 0;

    referenced.classId = AuthIdRelationId;
    referenced.objectId = owner;
    referenced.objectSubId = 0;

    recordSharedDependencyOn(&myself, &referenced, SHARED_DEPENDENCY_OWNER);
}

/*
 * shdepChangeDep
 *
 * Update shared dependency records to account for an updated referenced
 * object.  This is an internal workhorse for operations such as changing
 * an object's owner.
 *
 * There must be no more than one existing entry for the given dependent
 * object and dependency type!  So in practice this can only be used for
 * updating SHARED_DEPENDENCY_OWNER entries, which should have that property.
 *
 * If there is no previous entry, we assume it was referencing a PINned
 * object, so we create a new entry.  If the new referenced object is
 * PINned, we don't create an entry (and drop the old one, if any).
 *
 * sdepRel must be the pg_shdepend relation, already opened and suitably
 * locked.
 */
static void
shdepChangeDep(Relation sdepRel,
               Oid classid, Oid objid, int32 objsubid,
               Oid refclassid, Oid refobjid,
               SharedDependencyType deptype)
{
    Oid         dbid = classIdGetDbId(classid);
    HeapTuple   oldtup = NULL;
    HeapTuple   scantup;
    ScanKeyData key[4];
    SysScanDesc scan;

    /*
     * Make sure the new referenced object doesn't go away while we record the
     * dependency.
     */
    shdepLockAndCheckObject(refclassid, refobjid);

    /*
     * Look for a previous entry
     */
    ScanKeyInit(&key[0],
                Anum_pg_shdepend_dbid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(dbid));
    ScanKeyInit(&key[1],
                Anum_pg_shdepend_classid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(classid));
    ScanKeyInit(&key[2],
                Anum_pg_shdepend_objid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(objid));
    ScanKeyInit(&key[3],
                Anum_pg_shdepend_objsubid,
                BTEqualStrategyNumber, F_INT4EQ,
                Int32GetDatum(objsubid));

    scan = systable_beginscan(sdepRel, SharedDependDependerIndexId, true,
                              SnapshotNow, 4, key);

    while ((scantup = systable_getnext(scan)) != NULL)
    {
        /* Ignore if not of the target dependency type */
        if (((Form_pg_shdepend) GETSTRUCT(scantup))->deptype != deptype)
            continue;
        /* Caller screwed up if multiple matches */
        if (oldtup)
            elog(ERROR,
               "multiple pg_shdepend entries for object %u/%u/%d deptype %c",
                 classid, objid, objsubid, deptype);
        oldtup = heap_copytuple(scantup);
    }

    systable_endscan(scan);

    if (isSharedObjectPinned(refclassid, refobjid, sdepRel))
    {
        /* No new entry needed, so just delete existing entry if any */
        if (oldtup)
            simple_heap_delete(sdepRel, &oldtup->t_self);
    }
    else if (oldtup)
    {
        /* Need to update existing entry */
        Form_pg_shdepend shForm = (Form_pg_shdepend) GETSTRUCT(oldtup);

        /* Since oldtup is a copy, we can just modify it in-memory */
        shForm->refclassid = refclassid;
        shForm->refobjid = refobjid;

        simple_heap_update(sdepRel, &oldtup->t_self, oldtup);

        /* keep indexes current */
        CatalogUpdateIndexes(sdepRel, oldtup);
    }
    else
    {
        /* Need to insert new entry */
        Datum       values[Natts_pg_shdepend];
        bool        nulls[Natts_pg_shdepend];

        memset(nulls, false, sizeof(nulls));

        values[Anum_pg_shdepend_dbid - 1] = ObjectIdGetDatum(dbid);
        values[Anum_pg_shdepend_classid - 1] = ObjectIdGetDatum(classid);
        values[Anum_pg_shdepend_objid - 1] = ObjectIdGetDatum(objid);
        values[Anum_pg_shdepend_objsubid - 1] = Int32GetDatum(objsubid);

        values[Anum_pg_shdepend_refclassid - 1] = ObjectIdGetDatum(refclassid);
        values[Anum_pg_shdepend_refobjid - 1] = ObjectIdGetDatum(refobjid);
        values[Anum_pg_shdepend_deptype - 1] = CharGetDatum(deptype);

        /*
         * we are reusing oldtup just to avoid declaring a new variable, but
         * it's certainly a new tuple
         */
        oldtup = heap_form_tuple(RelationGetDescr(sdepRel), values, nulls);
        simple_heap_insert(sdepRel, oldtup);

        /* keep indexes current */
        CatalogUpdateIndexes(sdepRel, oldtup);
    }

    if (oldtup)
        heap_freetuple(oldtup);
}

/*
 * changeDependencyOnOwner
 *
 * Update the shared dependencies to account for the new owner.
 *
 * Note: we don't need an objsubid argument because only whole objects
 * have owners.
 */
void
changeDependencyOnOwner(Oid classId, Oid objectId, Oid newOwnerId)
{
    Relation    sdepRel;

    sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

    /* Adjust the SHARED_DEPENDENCY_OWNER entry */
    shdepChangeDep(sdepRel,
                   classId, objectId, 0,
                   AuthIdRelationId, newOwnerId,
                   SHARED_DEPENDENCY_OWNER);

    /*----------
     * There should never be a SHARED_DEPENDENCY_ACL entry for the owner,
     * so get rid of it if there is one.  This can happen if the new owner
     * was previously granted some rights to the object.
     *
     * This step is analogous to aclnewowner's removal of duplicate entries
     * in the ACL.  We have to do it to handle this scenario:
     *      A grants some rights on an object to B
     *      ALTER OWNER changes the object's owner to B
     *      ALTER OWNER changes the object's owner to C
     * The third step would remove all mention of B from the object's ACL,
     * but we'd still have a SHARED_DEPENDENCY_ACL for B if we did not do
     * things this way.
     *
     * The rule against having a SHARED_DEPENDENCY_ACL entry for the owner
     * allows us to fix things up in just this one place, without having
     * to make the various ALTER OWNER routines each know about it.
     *----------
     */
    shdepDropDependency(sdepRel, classId, objectId, 0, true,
                        AuthIdRelationId, newOwnerId,
                        SHARED_DEPENDENCY_ACL);

    heap_close(sdepRel, RowExclusiveLock);
}

/*
 * getOidListDiff
 *      Helper for updateAclDependencies.
 *
 * Takes two Oid arrays and removes elements that are common to both arrays,
 * leaving just those that are in one input but not the other.
 * We assume both arrays have been sorted and de-duped.
 */
static void
getOidListDiff(Oid *list1, int *nlist1, Oid *list2, int *nlist2)
{
    int         in1,
                in2,
                out1,
                out2;

    in1 = in2 = out1 = out2 = 0;
    while (in1 < *nlist1 && in2 < *nlist2)
    {
        if (list1[in1] == list2[in2])
        {
            /* skip over duplicates */
            in1++;
            in2++;
        }
        else if (list1[in1] < list2[in2])
        {
            /* list1[in1] is not in list2 */
            list1[out1++] = list1[in1++];
        }
        else
        {
            /* list2[in2] is not in list1 */
            list2[out2++] = list2[in2++];
        }
    }

    /* any remaining list1 entries are not in list2 */
    while (in1 < *nlist1)
    {
        list1[out1++] = list1[in1++];
    }

    /* any remaining list2 entries are not in list1 */
    while (in2 < *nlist2)
    {
        list2[out2++] = list2[in2++];
    }

    *nlist1 = out1;
    *nlist2 = out2;
}

/*
 * updateAclDependencies
 *      Update the pg_shdepend info for an object's ACL during GRANT/REVOKE.
 *
 * classId, objectId, objsubId: identify the object whose ACL this is
 * ownerId: role owning the object
 * noldmembers, oldmembers: array of roleids appearing in old ACL
 * nnewmembers, newmembers: array of roleids appearing in new ACL
 *
 * We calculate the differences between the new and old lists of roles,
 * and then insert or delete from pg_shdepend as appropriate.
 *
 * Note that we can't just insert all referenced roles blindly during GRANT,
 * because we would end up with duplicate registered dependencies.  We could
 * check for existence of the tuples before inserting, but that seems to be
 * more expensive than what we are doing here.  Likewise we can't just delete
 * blindly during REVOKE, because the user may still have other privileges.
 * It is also possible that REVOKE actually adds dependencies, due to
 * instantiation of a formerly implicit default ACL (although at present,
 * all such dependencies should be for the owning role, which we ignore here).
 *
 * NOTE: Both input arrays must be sorted and de-duped.  (Typically they
 * are extracted from an ACL array by aclmembers(), which takes care of
 * both requirements.)  The arrays are pfreed before return.
 */
void
updateAclDependencies(Oid classId, Oid objectId, int32 objsubId,
                      Oid ownerId,
                      int noldmembers, Oid *oldmembers,
                      int nnewmembers, Oid *newmembers)
{
    Relation    sdepRel;
    int         i;

    /*
     * Remove entries that are common to both lists; those represent existing
     * dependencies we don't need to change.
     *
     * OK to overwrite the inputs since we'll pfree them anyway.
     */
    getOidListDiff(oldmembers, &noldmembers, newmembers, &nnewmembers);

    if (noldmembers > 0 || nnewmembers > 0)
    {
        sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

        /* Add new dependencies that weren't already present */
        for (i = 0; i < nnewmembers; i++)
        {
            Oid         roleid = newmembers[i];

            /*
             * Skip the owner: he has an OWNER shdep entry instead. (This is
             * not just a space optimization; it makes ALTER OWNER easier. See
             * notes in changeDependencyOnOwner.)
             */
            if (roleid == ownerId)
                continue;

            /* Skip pinned roles; they don't need dependency entries */
            if (isSharedObjectPinned(AuthIdRelationId, roleid, sdepRel))
                continue;

            shdepAddDependency(sdepRel, classId, objectId, objsubId,
                               AuthIdRelationId, roleid,
                               SHARED_DEPENDENCY_ACL);
        }

        /* Drop no-longer-used old dependencies */
        for (i = 0; i < noldmembers; i++)
        {
            Oid         roleid = oldmembers[i];

            /* Skip the owner, same as above */
            if (roleid == ownerId)
                continue;

            /* Skip pinned roles */
            if (isSharedObjectPinned(AuthIdRelationId, roleid, sdepRel))
                continue;

            shdepDropDependency(sdepRel, classId, objectId, objsubId,
                                false,  /* exact match on objsubId */
                                AuthIdRelationId, roleid,
                                SHARED_DEPENDENCY_ACL);
        }

        heap_close(sdepRel, RowExclusiveLock);
    }

    if (oldmembers)
        pfree(oldmembers);
    if (newmembers)
        pfree(newmembers);
}

/*
 * A struct to keep track of dependencies found in other databases.
 */
typedef struct
{
    Oid         dbOid;
    int         count;
} remoteDep;

/*
 * checkSharedDependencies
 *
 * Check whether there are shared dependency entries for a given shared
 * object; return true if so.
 *
 * In addition, return a string containing a newline-separated list of object
 * descriptions that depend on the shared object, or NULL if none is found.
 * We actually return two such strings; the "detail" result is suitable for
 * returning to the client as an errdetail() string, and is limited in size.
 * The "detail_log" string is potentially much longer, and should be emitted
 * to the server log only.
 *
 * We can find three different kinds of dependencies: dependencies on objects
 * of the current database; dependencies on shared objects; and dependencies
 * on objects local to other databases.  We can (and do) provide descriptions
 * of the two former kinds of objects, but we can't do that for "remote"
 * objects, so we just provide a count of them.
 *
 * If we find a SHARED_DEPENDENCY_PIN entry, we can error out early.
 */
bool
checkSharedDependencies(Oid classId, Oid objectId,
                        char **detail_msg, char **detail_log_msg)
{
    Relation    sdepRel;
    ScanKeyData key[2];
    SysScanDesc scan;
    HeapTuple   tup;
    int         numReportedDeps = 0;
    int         numNotReportedDeps = 0;
    int         numNotReportedDbs = 0;
    List       *remDeps = NIL;
    ListCell   *cell;
    ObjectAddress object;
    StringInfoData descs;
    StringInfoData alldescs;

    /*
     * We limit the number of dependencies reported to the client to
     * MAX_REPORTED_DEPS, since client software may not deal well with
     * enormous error strings.  The server log always gets a full report.
     */
#define MAX_REPORTED_DEPS 100

    initStringInfo(&descs);
    initStringInfo(&alldescs);

    sdepRel = heap_open(SharedDependRelationId, AccessShareLock);

    ScanKeyInit(&key[0],
                Anum_pg_shdepend_refclassid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(classId));
    ScanKeyInit(&key[1],
                Anum_pg_shdepend_refobjid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(objectId));

    scan = systable_beginscan(sdepRel, SharedDependReferenceIndexId, true,
                              SnapshotNow, 2, key);

    while (HeapTupleIsValid(tup = systable_getnext(scan)))
    {
        Form_pg_shdepend sdepForm = (Form_pg_shdepend) GETSTRUCT(tup);

        /* This case can be dispatched quickly */
        if (sdepForm->deptype == SHARED_DEPENDENCY_PIN)
        {
            object.classId = classId;
            object.objectId = objectId;
            object.objectSubId = 0;
            ereport(ERROR,
                    (errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
                     errmsg("cannot drop %s because it is required by the database system",
                            getObjectDescription(&object))));
        }

        object.classId = sdepForm->classid;
        object.objectId = sdepForm->objid;
        object.objectSubId = sdepForm->objsubid;

        /*
         * If it's a dependency local to this database or it's a shared
         * object, describe it.
         *
         * If it's a remote dependency, keep track of it so we can report the
         * number of them later.
         */
        if (sdepForm->dbid == MyDatabaseId)
        {
            if (numReportedDeps < MAX_REPORTED_DEPS)
            {
                numReportedDeps++;
                storeObjectDescription(&descs, LOCAL_OBJECT, &object,
                                       sdepForm->deptype, 0);
            }
            else
                numNotReportedDeps++;
            storeObjectDescription(&alldescs, LOCAL_OBJECT, &object,
                                   sdepForm->deptype, 0);
        }
        else if (sdepForm->dbid == InvalidOid)
        {
            if (numReportedDeps < MAX_REPORTED_DEPS)
            {
                numReportedDeps++;
                storeObjectDescription(&descs, SHARED_OBJECT, &object,
                                       sdepForm->deptype, 0);
            }
            else
                numNotReportedDeps++;
            storeObjectDescription(&alldescs, SHARED_OBJECT, &object,
                                   sdepForm->deptype, 0);
        }
        else
        {
            /* It's not local nor shared, so it must be remote. */
            remoteDep  *dep;
            bool        stored = false;

            /*
             * XXX this info is kept on a simple List.  Maybe it's not good
             * for performance, but using a hash table seems needlessly
             * complex.  The expected number of databases is not high anyway,
             * I suppose.
             */
            foreach(cell, remDeps)
            {
                dep = lfirst(cell);
                if (dep->dbOid == sdepForm->dbid)
                {
                    dep->count++;
                    stored = true;
                    break;
                }
            }
            if (!stored)
            {
                dep = (remoteDep *) palloc(sizeof(remoteDep));
                dep->dbOid = sdepForm->dbid;
                dep->count = 1;
                remDeps = lappend(remDeps, dep);
            }
        }
    }

    systable_endscan(scan);

    heap_close(sdepRel, AccessShareLock);

    /*
     * Summarize dependencies in remote databases.
     */
    foreach(cell, remDeps)
    {
        remoteDep  *dep = lfirst(cell);

        object.classId = DatabaseRelationId;
        object.objectId = dep->dbOid;
        object.objectSubId = 0;

        if (numReportedDeps < MAX_REPORTED_DEPS)
        {
            numReportedDeps++;
            storeObjectDescription(&descs, REMOTE_OBJECT, &object,
                                   SHARED_DEPENDENCY_INVALID, dep->count);
        }
        else
            numNotReportedDbs++;
        storeObjectDescription(&alldescs, REMOTE_OBJECT, &object,
                               SHARED_DEPENDENCY_INVALID, dep->count);
    }

    list_free_deep(remDeps);

    if (descs.len == 0)
    {
        pfree(descs.data);
        pfree(alldescs.data);
        *detail_msg = *detail_log_msg = NULL;
        return false;
    }

    if (numNotReportedDeps > 0)
        appendStringInfo(&descs, ngettext("\nand %d other object "
                                          "(see server log for list)",
                                          "\nand %d other objects "
                                          "(see server log for list)",
                                          numNotReportedDeps),
                         numNotReportedDeps);
    if (numNotReportedDbs > 0)
        appendStringInfo(&descs, ngettext("\nand objects in %d other database "
                                          "(see server log for list)",
                                       "\nand objects in %d other databases "
                                          "(see server log for list)",
                                          numNotReportedDbs),
                         numNotReportedDbs);

    *detail_msg = descs.data;
    *detail_log_msg = alldescs.data;
    return true;
}

/*
 * copyTemplateDependencies
 *
 * Routine to create the initial shared dependencies of a new database.
 * We simply copy the dependencies from the template database.
 */
void
copyTemplateDependencies(Oid templateDbId, Oid newDbId)
{
    Relation    sdepRel;
    TupleDesc   sdepDesc;
    ScanKeyData key[1];
    SysScanDesc scan;
    HeapTuple   tup;
    CatalogIndexState indstate;
    Datum       values[Natts_pg_shdepend];
    bool        nulls[Natts_pg_shdepend];
    bool        replace[Natts_pg_shdepend];

    sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);
    sdepDesc = RelationGetDescr(sdepRel);

    indstate = CatalogOpenIndexes(sdepRel);

    /* Scan all entries with dbid = templateDbId */
    ScanKeyInit(&key[0],
                Anum_pg_shdepend_dbid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(templateDbId));

    scan = systable_beginscan(sdepRel, SharedDependDependerIndexId, true,
                              SnapshotNow, 1, key);

    /* Set up to copy the tuples except for inserting newDbId */
    memset(values, 0, sizeof(values));
    memset(nulls, false, sizeof(nulls));
    memset(replace, false, sizeof(replace));

    replace[Anum_pg_shdepend_dbid - 1] = true;
    values[Anum_pg_shdepend_dbid - 1] = ObjectIdGetDatum(newDbId);

    /*
     * Copy the entries of the original database, changing the database Id to
     * that of the new database.  Note that because we are not copying rows
     * with dbId == 0 (ie, rows describing dependent shared objects) we won't
     * copy the ownership dependency of the template database itself; this is
     * what we want.
     */
    while (HeapTupleIsValid(tup = systable_getnext(scan)))
    {
        HeapTuple   newtup;

        newtup = heap_modify_tuple(tup, sdepDesc, values, nulls, replace);
        simple_heap_insert(sdepRel, newtup);

        /* Keep indexes current */
        CatalogIndexInsert(indstate, newtup);

        heap_freetuple(newtup);
    }

    systable_endscan(scan);

    CatalogCloseIndexes(indstate);
    heap_close(sdepRel, RowExclusiveLock);
}

/*
 * dropDatabaseDependencies
 *
 * Delete pg_shdepend entries corresponding to a database that's being
 * dropped.
 */
void
dropDatabaseDependencies(Oid databaseId)
{
    Relation    sdepRel;
    ScanKeyData key[1];
    SysScanDesc scan;
    HeapTuple   tup;

    sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

    /*
     * First, delete all the entries that have the database Oid in the dbid
     * field.
     */
    ScanKeyInit(&key[0],
                Anum_pg_shdepend_dbid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(databaseId));
    /* We leave the other index fields unspecified */

    scan = systable_beginscan(sdepRel, SharedDependDependerIndexId, true,
                              SnapshotNow, 1, key);

    while (HeapTupleIsValid(tup = systable_getnext(scan)))
    {
        simple_heap_delete(sdepRel, &tup->t_self);
    }

    systable_endscan(scan);

    /* Now delete all entries corresponding to the database itself */
    shdepDropDependency(sdepRel, DatabaseRelationId, databaseId, 0, true,
                        InvalidOid, InvalidOid,
                        SHARED_DEPENDENCY_INVALID);

    heap_close(sdepRel, RowExclusiveLock);
}

/*
 * deleteSharedDependencyRecordsFor
 *
 * Delete all pg_shdepend entries corresponding to an object that's being
 * dropped or modified.  The object is assumed to be either a shared object
 * or local to the current database (the classId tells us which).
 *
 * If objectSubId is zero, we are deleting a whole object, so get rid of
 * pg_shdepend entries for subobjects as well.
 */
void
deleteSharedDependencyRecordsFor(Oid classId, Oid objectId, int32 objectSubId)
{
    Relation    sdepRel;

    sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

    shdepDropDependency(sdepRel, classId, objectId, objectSubId,
                        (objectSubId == 0),
                        InvalidOid, InvalidOid,
                        SHARED_DEPENDENCY_INVALID);

    heap_close(sdepRel, RowExclusiveLock);
}

/*
 * shdepAddDependency
 *      Internal workhorse for inserting into pg_shdepend
 *
 * sdepRel must be the pg_shdepend relation, already opened and suitably
 * locked.
 */
static void
shdepAddDependency(Relation sdepRel,
                   Oid classId, Oid objectId, int32 objsubId,
                   Oid refclassId, Oid refobjId,
                   SharedDependencyType deptype)
{
    HeapTuple   tup;
    Datum       values[Natts_pg_shdepend];
    bool        nulls[Natts_pg_shdepend];

    /*
     * Make sure the object doesn't go away while we record the dependency on
     * it.  DROP routines should lock the object exclusively before they check
     * shared dependencies.
     */
    shdepLockAndCheckObject(refclassId, refobjId);

    memset(nulls, false, sizeof(nulls));

    /*
     * Form the new tuple and record the dependency.
     */
    values[Anum_pg_shdepend_dbid - 1] = ObjectIdGetDatum(classIdGetDbId(classId));
    values[Anum_pg_shdepend_classid - 1] = ObjectIdGetDatum(classId);
    values[Anum_pg_shdepend_objid - 1] = ObjectIdGetDatum(objectId);
    values[Anum_pg_shdepend_objsubid - 1] = Int32GetDatum(objsubId);

    values[Anum_pg_shdepend_refclassid - 1] = ObjectIdGetDatum(refclassId);
    values[Anum_pg_shdepend_refobjid - 1] = ObjectIdGetDatum(refobjId);
    values[Anum_pg_shdepend_deptype - 1] = CharGetDatum(deptype);

    tup = heap_form_tuple(sdepRel->rd_att, values, nulls);

    simple_heap_insert(sdepRel, tup);

    /* keep indexes current */
    CatalogUpdateIndexes(sdepRel, tup);

    /* clean up */
    heap_freetuple(tup);
}

/*
 * shdepDropDependency
 *      Internal workhorse for deleting entries from pg_shdepend.
 *
 * We drop entries having the following properties:
 *  dependent object is the one identified by classId/objectId/objsubId
 *  if refclassId isn't InvalidOid, it must match the entry's refclassid
 *  if refobjId isn't InvalidOid, it must match the entry's refobjid
 *  if deptype isn't SHARED_DEPENDENCY_INVALID, it must match entry's deptype
 *
 * If drop_subobjects is true, we ignore objsubId and consider all entries
 * matching classId/objectId.
 *
 * sdepRel must be the pg_shdepend relation, already opened and suitably
 * locked.
 */
static void
shdepDropDependency(Relation sdepRel,
                    Oid classId, Oid objectId, int32 objsubId,
                    bool drop_subobjects,
                    Oid refclassId, Oid refobjId,
                    SharedDependencyType deptype)
{
    ScanKeyData key[4];
    int         nkeys;
    SysScanDesc scan;
    HeapTuple   tup;

    /* Scan for entries matching the dependent object */
    ScanKeyInit(&key[0],
                Anum_pg_shdepend_dbid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(classIdGetDbId(classId)));
    ScanKeyInit(&key[1],
                Anum_pg_shdepend_classid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(classId));
    ScanKeyInit(&key[2],
                Anum_pg_shdepend_objid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(objectId));
    if (drop_subobjects)
        nkeys = 3;
    else
    {
        ScanKeyInit(&key[3],
                    Anum_pg_shdepend_objsubid,
                    BTEqualStrategyNumber, F_INT4EQ,
                    Int32GetDatum(objsubId));
        nkeys = 4;
    }

    scan = systable_beginscan(sdepRel, SharedDependDependerIndexId, true,
                              SnapshotNow, nkeys, key);

    while (HeapTupleIsValid(tup = systable_getnext(scan)))
    {
        Form_pg_shdepend shdepForm = (Form_pg_shdepend) GETSTRUCT(tup);

        /* Filter entries according to additional parameters */
        if (OidIsValid(refclassId) && shdepForm->refclassid != refclassId)
            continue;
        if (OidIsValid(refobjId) && shdepForm->refobjid != refobjId)
            continue;
        if (deptype != SHARED_DEPENDENCY_INVALID &&
            shdepForm->deptype != deptype)
            continue;

        /* OK, delete it */
        simple_heap_delete(sdepRel, &tup->t_self);
    }

    systable_endscan(scan);
}

/*
 * classIdGetDbId
 *
 * Get the database Id that should be used in pg_shdepend, given the OID
 * of the catalog containing the object.  For shared objects, it's 0
 * (InvalidOid); for all other objects, it's the current database Id.
 */
static Oid
classIdGetDbId(Oid classId)
{
    Oid         dbId;

    if (IsSharedRelation(classId))
        dbId = InvalidOid;
    else
        dbId = MyDatabaseId;

    return dbId;
}

/*
 * shdepLockAndCheckObject
 *
 * Lock the object that we are about to record a dependency on.
 * After it's locked, verify that it hasn't been dropped while we
 * weren't looking.  If the object has been dropped, this function
 * does not return!
 */
void
shdepLockAndCheckObject(Oid classId, Oid objectId)
{
    /* AccessShareLock should be OK, since we are not modifying the object */
    LockSharedObject(classId, objectId, 0, AccessShareLock);

    switch (classId)
    {
        case AuthIdRelationId:
            if (!SearchSysCacheExists1(AUTHOID, ObjectIdGetDatum(objectId)))
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                         errmsg("role %u was concurrently dropped",
                                objectId)));
            break;

            /*
             * Currently, this routine need not support any other shared
             * object types besides roles.  If we wanted to record explicit
             * dependencies on databases or tablespaces, we'd need code along
             * these lines:
             */
#ifdef NOT_USED
        case TableSpaceRelationId:
            {
                /* For lack of a syscache on pg_tablespace, do this: */
                char       *tablespace = get_tablespace_name(objectId);

                if (tablespace == NULL)
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_OBJECT),
                             errmsg("tablespace %u was concurrently dropped",
                                    objectId)));
                pfree(tablespace);
                break;
            }
#endif

        case DatabaseRelationId:
            {
                /* For lack of a syscache on pg_database, do this: */
                char       *database = get_database_name(objectId);

                if (database == NULL)
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_OBJECT),
                             errmsg("database %u was concurrently dropped",
                                    objectId)));
                pfree(database);
                break;
            }


        default:
            elog(ERROR, "unrecognized shared classId: %u", classId);
    }
}


/*
 * storeObjectDescription
 *      Append the description of a dependent object to "descs"
 *
 * While searching for dependencies of a shared object, we stash the
 * descriptions of dependent objects we find in a single string, which we
 * later pass to ereport() in the DETAIL field when somebody attempts to
 * drop a referenced shared object.
 *
 * When type is LOCAL_OBJECT or SHARED_OBJECT, we expect object to be the
 * dependent object, deptype is the dependency type, and count is not used.
 * When type is REMOTE_OBJECT, we expect object to be the database object,
 * and count to be nonzero; deptype is not used in this case.
 */
static void
storeObjectDescription(StringInfo descs, objectType type,
                       ObjectAddress *object,
                       SharedDependencyType deptype,
                       int count)
{
    char       *objdesc = getObjectDescription(object);

    /* separate entries with a newline */
    if (descs->len != 0)
        appendStringInfoChar(descs, '\n');

    switch (type)
    {
        case LOCAL_OBJECT:
        case SHARED_OBJECT:
            if (deptype == SHARED_DEPENDENCY_OWNER)
                appendStringInfo(descs, _("owner of %s"), objdesc);
            else if (deptype == SHARED_DEPENDENCY_ACL)
                appendStringInfo(descs, _("privileges for %s"), objdesc);
            else
                elog(ERROR, "unrecognized dependency type: %d",
                     (int) deptype);
            break;

        case REMOTE_OBJECT:
            /* translator: %s will always be "database %s" */
            appendStringInfo(descs, ngettext("%d object in %s",
                                             "%d objects in %s",
                                             count),
                             count, objdesc);
            break;

        default:
            elog(ERROR, "unrecognized object type: %d", type);
    }

    pfree(objdesc);
}


/*
 * isSharedObjectPinned
 *      Return whether a given shared object has a SHARED_DEPENDENCY_PIN entry.
 *
 * sdepRel must be the pg_shdepend relation, already opened and suitably
 * locked.
 */
static bool
isSharedObjectPinned(Oid classId, Oid objectId, Relation sdepRel)
{
    bool        result = false;
    ScanKeyData key[2];
    SysScanDesc scan;
    HeapTuple   tup;

    ScanKeyInit(&key[0],
                Anum_pg_shdepend_refclassid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(classId));
    ScanKeyInit(&key[1],
                Anum_pg_shdepend_refobjid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(objectId));

    scan = systable_beginscan(sdepRel, SharedDependReferenceIndexId, true,
                              SnapshotNow, 2, key);

    /*
     * Since we won't generate additional pg_shdepend entries for pinned
     * objects, there can be at most one entry referencing a pinned object.
     * Hence, it's sufficient to look at the first returned tuple; we don't
     * need to loop.
     */
    tup = systable_getnext(scan);
    if (HeapTupleIsValid(tup))
    {
        Form_pg_shdepend shdepForm = (Form_pg_shdepend) GETSTRUCT(tup);

        if (shdepForm->deptype == SHARED_DEPENDENCY_PIN)
            result = true;
    }

    systable_endscan(scan);

    return result;
}

/*
 * shdepDropOwned
 *
 * Drop the objects owned by any one of the given RoleIds.  If a role has
 * access to an object, the grant will be removed as well (but the object
 * will not, of course).
 *
 * We can revoke grants immediately while doing the scan, but drops are
 * saved up and done all at once with performMultipleDeletions.  This
 * is necessary so that we don't get failures from trying to delete
 * interdependent objects in the wrong order.
 */
void
shdepDropOwned(List *roleids, DropBehavior behavior)
{
    Relation    sdepRel;
    ListCell   *cell;
    ObjectAddresses *deleteobjs;

    deleteobjs = new_object_addresses();

    /*
     * We don't need this strong a lock here, but we'll call routines that
     * acquire RowExclusiveLock.  Better get that right now to avoid potential
     * deadlock failures.
     */
    sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

    /*
     * For each role, find the dependent objects and drop them using the
     * regular (non-shared) dependency management.
     */
    foreach(cell, roleids)
    {
        Oid         roleid = lfirst_oid(cell);
        ScanKeyData key[2];
        SysScanDesc scan;
        HeapTuple   tuple;

        /* Doesn't work for pinned objects */
        if (isSharedObjectPinned(AuthIdRelationId, roleid, sdepRel))
        {
            ObjectAddress obj;

            obj.classId = AuthIdRelationId;
            obj.objectId = roleid;
            obj.objectSubId = 0;

            ereport(ERROR,
                    (errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
                   errmsg("cannot drop objects owned by %s because they are "
                          "required by the database system",
                          getObjectDescription(&obj))));
        }

        ScanKeyInit(&key[0],
                    Anum_pg_shdepend_refclassid,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(AuthIdRelationId));
        ScanKeyInit(&key[1],
                    Anum_pg_shdepend_refobjid,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(roleid));

        scan = systable_beginscan(sdepRel, SharedDependReferenceIndexId, true,
                                  SnapshotNow, 2, key);

        while ((tuple = systable_getnext(scan)) != NULL)
        {
            Form_pg_shdepend sdepForm = (Form_pg_shdepend) GETSTRUCT(tuple);
            ObjectAddress obj;

            /*
             * We only operate on shared objects and objects in the current
             * database
             */
            if (sdepForm->dbid != MyDatabaseId &&
                sdepForm->dbid != InvalidOid)
                continue;

            switch (sdepForm->deptype)
            {
                    /* Shouldn't happen */
                case SHARED_DEPENDENCY_PIN:
                case SHARED_DEPENDENCY_INVALID:
                    elog(ERROR, "unexpected dependency type");
                    break;
                case SHARED_DEPENDENCY_ACL:
                    RemoveRoleFromObjectACL(roleid,
                                            sdepForm->classid,
                                            sdepForm->objid);
                    break;
                case SHARED_DEPENDENCY_OWNER:
                    /* If a local object, save it for deletion below */
                    if (sdepForm->dbid == MyDatabaseId)
                    {
                        obj.classId = sdepForm->classid;
                        obj.objectId = sdepForm->objid;
                        obj.objectSubId = sdepForm->objsubid;
                        add_exact_object_address(&obj, deleteobjs);
                    }
                    break;
            }
        }

        systable_endscan(scan);
    }

    /* the dependency mechanism does the actual work */
    performMultipleDeletions(deleteobjs, behavior, 0);

    heap_close(sdepRel, RowExclusiveLock);

    free_object_addresses(deleteobjs);
}

/*
 * shdepReassignOwned
 *
 * Change the owner of objects owned by any of the roles in roleids to
 * newrole.  Grants are not touched.
 */
void
shdepReassignOwned(List *roleids, Oid newrole)
{
    Relation    sdepRel;
    ListCell   *cell;

    /*
     * We don't need this strong a lock here, but we'll call routines that
     * acquire RowExclusiveLock.  Better get that right now to avoid potential
     * deadlock problems.
     */
    sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

    foreach(cell, roleids)
    {
        SysScanDesc scan;
        ScanKeyData key[2];
        HeapTuple   tuple;
        Oid         roleid = lfirst_oid(cell);

        /* Refuse to work on pinned roles */
        if (isSharedObjectPinned(AuthIdRelationId, roleid, sdepRel))
        {
            ObjectAddress obj;

            obj.classId = AuthIdRelationId;
            obj.objectId = roleid;
            obj.objectSubId = 0;

            ereport(ERROR,
                    (errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
                     errmsg("cannot reassign ownership of objects owned by %s because they are required by the database system",
                            getObjectDescription(&obj))));

            /*
             * There's no need to tell the whole truth, which is that we
             * didn't track these dependencies at all ...
             */
        }

        ScanKeyInit(&key[0],
                    Anum_pg_shdepend_refclassid,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(AuthIdRelationId));
        ScanKeyInit(&key[1],
                    Anum_pg_shdepend_refobjid,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(roleid));

        scan = systable_beginscan(sdepRel, SharedDependReferenceIndexId, true,
                                  SnapshotNow, 2, key);

        while ((tuple = systable_getnext(scan)) != NULL)
        {
            Form_pg_shdepend sdepForm = (Form_pg_shdepend) GETSTRUCT(tuple);

            /*
             * We only operate on shared objects and objects in the current
             * database
             */
            if (sdepForm->dbid != MyDatabaseId &&
                sdepForm->dbid != InvalidOid)
                continue;

            /* Unexpected because we checked for pins above */
            if (sdepForm->deptype == SHARED_DEPENDENCY_PIN)
                elog(ERROR, "unexpected shared pin");

            /* We leave non-owner dependencies alone */
            if (sdepForm->deptype != SHARED_DEPENDENCY_OWNER)
                continue;

            /* Issue the appropriate ALTER OWNER call */
            switch (sdepForm->classid)
            {
                case TypeRelationId:
                    AlterTypeOwnerInternal(sdepForm->objid, newrole, true);
                    break;

                case NamespaceRelationId:
                    AlterSchemaOwner_oid(sdepForm->objid, newrole);
                    break;

                case RelationRelationId:

                    /*
                     * Pass recursing = true so that we don't fail on indexes,
                     * owned sequences, etc when we happen to visit them
                     * before their parent table.
                     */
                    ATExecChangeOwner(sdepForm->objid, newrole, true, AccessExclusiveLock);
                    break;

                case DefaultAclRelationId:

                    /*
                     * Ignore default ACLs; they should be handled by DROP
                     * OWNED, not REASSIGN OWNED.
                     */
                    break;

                case ForeignServerRelationId:
                    AlterForeignServerOwner_oid(sdepForm->objid, newrole);
                    break;

                case ForeignDataWrapperRelationId:
                    AlterForeignDataWrapperOwner_oid(sdepForm->objid, newrole);
                    break;

                case EventTriggerRelationId:
                    AlterEventTriggerOwner_oid(sdepForm->objid, newrole);
                    break;

                /* Generic alter owner cases */
                case CollationRelationId:
                case ConversionRelationId:
                case OperatorRelationId:
                case ProcedureRelationId:
                case LanguageRelationId:
                case LargeObjectRelationId:
                case OperatorFamilyRelationId:
                case OperatorClassRelationId:
                case ExtensionRelationId:
                case TableSpaceRelationId:
                case DatabaseRelationId:
                    {
                        Oid         classId = sdepForm->classid;
                        Relation    catalog;

                        if (classId == LargeObjectRelationId)
                            classId = LargeObjectMetadataRelationId;

                        catalog = heap_open(classId, RowExclusiveLock);

                        AlterObjectOwner_internal(catalog, sdepForm->objid,
                                                  newrole);

                        heap_close(catalog, NoLock);
                    }
                    break;

                default:
                    elog(ERROR, "unexpected classid %u", sdepForm->classid);
                    break;
            }
            /* Make sure the next iteration will see my changes */
            CommandCounterIncrement();
        }

        systable_endscan(scan);
    }

    heap_close(sdepRel, RowExclusiveLock);
}