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/*-------------------------------------------------------------------------
*
* portalmem.c
* backend portal memory management
*
* Portals are objects representing the execution state of a query.
* This module provides memory management services for portals, but it
* doesn't actually run the executor for them.
*
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/utils/mmgr/portalmem.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "commands/portalcmds.h"
#include "miscadmin.h"
#include "storage/ipc.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/snapmgr.h"
#include "utils/timestamp.h"
/*
* Estimate of the maximum number of open portals a user would have,
* used in initially sizing the PortalHashTable in EnablePortalManager().
* Since the hash table can expand, there's no need to make this overly
* generous, and keeping it small avoids unnecessary overhead in the
* hash_seq_search() calls executed during transaction end.
*/
#define PORTALS_PER_USER 16
/* ----------------
* Global state
* ----------------
*/
#define MAX_PORTALNAME_LEN NAMEDATALEN
typedef struct portalhashent
{
char portalname[MAX_PORTALNAME_LEN];
Portal portal;
} PortalHashEnt;
static HTAB *PortalHashTable = NULL;
#define PortalHashTableLookup(NAME, PORTAL) \
do { \
PortalHashEnt *hentry; \
\
hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
(NAME), HASH_FIND, NULL); \
if (hentry) \
PORTAL = hentry->portal; \
else \
PORTAL = NULL; \
} while(0)
#define PortalHashTableInsert(PORTAL, NAME) \
do { \
PortalHashEnt *hentry; bool found; \
\
hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
(NAME), HASH_ENTER, &found); \
if (found) \
elog(ERROR, "duplicate portal name"); \
hentry->portal = PORTAL; \
/* To avoid duplicate storage, make PORTAL->name point to htab entry */ \
PORTAL->name = hentry->portalname; \
} while(0)
#define PortalHashTableDelete(PORTAL) \
do { \
PortalHashEnt *hentry; \
\
hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
PORTAL->name, HASH_REMOVE, NULL); \
if (hentry == NULL) \
elog(WARNING, "trying to delete portal name that does not exist"); \
} while(0)
static MemoryContext TopPortalContext = NULL;
/* ----------------------------------------------------------------
* public portal interface functions
* ----------------------------------------------------------------
*/
/*
* EnablePortalManager
* Enables the portal management module at backend startup.
*/
void
EnablePortalManager(void)
{
HASHCTL ctl;
Assert(TopPortalContext == NULL);
TopPortalContext = AllocSetContextCreate(TopMemoryContext,
"TopPortalContext",
ALLOCSET_DEFAULT_SIZES);
ctl.keysize = MAX_PORTALNAME_LEN;
ctl.entrysize = sizeof(PortalHashEnt);
/*
* use PORTALS_PER_USER as a guess of how many hash table entries to
* create, initially
*/
PortalHashTable = hash_create("Portal hash", PORTALS_PER_USER,
&ctl, HASH_ELEM);
}
/*
* GetPortalByName
* Returns a portal given a portal name, or NULL if name not found.
*/
Portal
GetPortalByName(const char *name)
{
Portal portal;
if (PointerIsValid(name))
PortalHashTableLookup(name, portal);
else
portal = NULL;
return portal;
}
/*
* PortalGetPrimaryStmt
* Get the "primary" stmt within a portal, ie, the one marked canSetTag.
*
* Returns NULL if no such stmt. If multiple PlannedStmt structs within the
* portal are marked canSetTag, returns the first one. Neither of these
* cases should occur in present usages of this function.
*/
PlannedStmt *
PortalGetPrimaryStmt(Portal portal)
{
ListCell *lc;
foreach(lc, portal->stmts)
{
PlannedStmt *stmt = lfirst_node(PlannedStmt, lc);
if (stmt->canSetTag)
return stmt;
}
return NULL;
}
/*
* CreatePortal
* Returns a new portal given a name.
*
* allowDup: if true, automatically drop any pre-existing portal of the
* same name (if false, an error is raised).
*
* dupSilent: if true, don't even emit a WARNING.
*/
Portal
CreatePortal(const char *name, bool allowDup, bool dupSilent)
{
Portal portal;
AssertArg(PointerIsValid(name));
portal = GetPortalByName(name);
if (PortalIsValid(portal))
{
if (!allowDup)
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_CURSOR),
errmsg("cursor \"%s\" already exists", name)));
if (!dupSilent)
ereport(WARNING,
(errcode(ERRCODE_DUPLICATE_CURSOR),
errmsg("closing existing cursor \"%s\"",
name)));
PortalDrop(portal, false);
}
/* make new portal structure */
portal = (Portal) MemoryContextAllocZero(TopPortalContext, sizeof *portal);
/* initialize portal context; typically it won't store much */
portal->portalContext = AllocSetContextCreate(TopPortalContext,
"PortalContext",
ALLOCSET_SMALL_SIZES);
/* create a resource owner for the portal */
portal->resowner = ResourceOwnerCreate(CurTransactionResourceOwner,
"Portal");
/* initialize portal fields that don't start off zero */
portal->status = PORTAL_NEW;
portal->cleanup = PortalCleanup;
portal->createSubid = GetCurrentSubTransactionId();
portal->activeSubid = portal->createSubid;
portal->strategy = PORTAL_MULTI_QUERY;
portal->cursorOptions = CURSOR_OPT_NO_SCROLL;
portal->atStart = true;
portal->atEnd = true; /* disallow fetches until query is set */
portal->visible = true;
portal->creation_time = GetCurrentStatementStartTimestamp();
/* put portal in table (sets portal->name) */
PortalHashTableInsert(portal, name);
/* reuse portal->name copy */
MemoryContextSetIdentifier(portal->portalContext, portal->name);
return portal;
}
/*
* CreateNewPortal
* Create a new portal, assigning it a random nonconflicting name.
*/
Portal
CreateNewPortal(void)
{
static unsigned int unnamed_portal_count = 0;
char portalname[MAX_PORTALNAME_LEN];
/* Select a nonconflicting name */
for (;;)
{
unnamed_portal_count++;
sprintf(portalname, "<unnamed portal %u>", unnamed_portal_count);
if (GetPortalByName(portalname) == NULL)
break;
}
return CreatePortal(portalname, false, false);
}
/*
* PortalDefineQuery
* A simple subroutine to establish a portal's query.
*
* Notes: as of PG 8.4, caller MUST supply a sourceText string; it is not
* allowed anymore to pass NULL. (If you really don't have source text,
* you can pass a constant string, perhaps "(query not available)".)
*
* commandTag shall be NULL if and only if the original query string
* (before rewriting) was an empty string. Also, the passed commandTag must
* be a pointer to a constant string, since it is not copied.
*
* If cplan is provided, then it is a cached plan containing the stmts, and
* the caller must have done GetCachedPlan(), causing a refcount increment.
* The refcount will be released when the portal is destroyed.
*
* If cplan is NULL, then it is the caller's responsibility to ensure that
* the passed plan trees have adequate lifetime. Typically this is done by
* copying them into the portal's context.
*
* The caller is also responsible for ensuring that the passed prepStmtName
* (if not NULL) and sourceText have adequate lifetime.
*
* NB: this function mustn't do much beyond storing the passed values; in
* particular don't do anything that risks elog(ERROR). If that were to
* happen here before storing the cplan reference, we'd leak the plancache
* refcount that the caller is trying to hand off to us.
*/
void
PortalDefineQuery(Portal portal,
const char *prepStmtName,
const char *sourceText,
const char *commandTag,
List *stmts,
CachedPlan *cplan)
{
AssertArg(PortalIsValid(portal));
AssertState(portal->status == PORTAL_NEW);
AssertArg(sourceText != NULL);
AssertArg(commandTag != NULL || stmts == NIL);
portal->prepStmtName = prepStmtName;
portal->sourceText = sourceText;
portal->commandTag = commandTag;
portal->stmts = stmts;
portal->cplan = cplan;
portal->status = PORTAL_DEFINED;
}
/*
* PortalReleaseCachedPlan
* Release a portal's reference to its cached plan, if any.
*/
static void
PortalReleaseCachedPlan(Portal portal)
{
if (portal->cplan)
{
ReleaseCachedPlan(portal->cplan, false);
portal->cplan = NULL;
/*
* We must also clear portal->stmts which is now a dangling reference
* to the cached plan's plan list. This protects any code that might
* try to examine the Portal later.
*/
portal->stmts = NIL;
}
}
/*
* PortalCreateHoldStore
* Create the tuplestore for a portal.
*/
void
PortalCreateHoldStore(Portal portal)
{
MemoryContext oldcxt;
Assert(portal->holdContext == NULL);
Assert(portal->holdStore == NULL);
Assert(portal->holdSnapshot == NULL);
/*
* Create the memory context that is used for storage of the tuple set.
* Note this is NOT a child of the portal's portalContext.
*/
portal->holdContext =
AllocSetContextCreate(TopPortalContext,
"PortalHoldContext",
ALLOCSET_DEFAULT_SIZES);
/*
* Create the tuple store, selecting cross-transaction temp files, and
* enabling random access only if cursor requires scrolling.
*
* XXX: Should maintenance_work_mem be used for the portal size?
*/
oldcxt = MemoryContextSwitchTo(portal->holdContext);
portal->holdStore =
tuplestore_begin_heap(portal->cursorOptions & CURSOR_OPT_SCROLL,
true, work_mem);
MemoryContextSwitchTo(oldcxt);
}
/*
* PinPortal
* Protect a portal from dropping.
*
* A pinned portal is still unpinned and dropped at transaction or
* subtransaction abort.
*/
void
PinPortal(Portal portal)
{
if (portal->portalPinned)
elog(ERROR, "portal already pinned");
portal->portalPinned = true;
}
void
UnpinPortal(Portal portal)
{
if (!portal->portalPinned)
elog(ERROR, "portal not pinned");
portal->portalPinned = false;
}
/*
* MarkPortalActive
* Transition a portal from READY to ACTIVE state.
*
* NOTE: never set portal->status = PORTAL_ACTIVE directly; call this instead.
*/
void
MarkPortalActive(Portal portal)
{
/* For safety, this is a runtime test not just an Assert */
if (portal->status != PORTAL_READY)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("portal \"%s\" cannot be run", portal->name)));
/* Perform the state transition */
portal->status = PORTAL_ACTIVE;
portal->activeSubid = GetCurrentSubTransactionId();
}
/*
* MarkPortalDone
* Transition a portal from ACTIVE to DONE state.
*
* NOTE: never set portal->status = PORTAL_DONE directly; call this instead.
*/
void
MarkPortalDone(Portal portal)
{
/* Perform the state transition */
Assert(portal->status == PORTAL_ACTIVE);
portal->status = PORTAL_DONE;
/*
* Allow portalcmds.c to clean up the state it knows about. We might as
* well do that now, since the portal can't be executed any more.
*
* In some cases involving execution of a ROLLBACK command in an already
* aborted transaction, this is necessary, or we'd reach AtCleanup_Portals
* with the cleanup hook still unexecuted.
*/
if (PointerIsValid(portal->cleanup))
{
portal->cleanup(portal);
portal->cleanup = NULL;
}
}
/*
* MarkPortalFailed
* Transition a portal into FAILED state.
*
* NOTE: never set portal->status = PORTAL_FAILED directly; call this instead.
*/
void
MarkPortalFailed(Portal portal)
{
/* Perform the state transition */
Assert(portal->status != PORTAL_DONE);
portal->status = PORTAL_FAILED;
/*
* Allow portalcmds.c to clean up the state it knows about. We might as
* well do that now, since the portal can't be executed any more.
*
* In some cases involving cleanup of an already aborted transaction, this
* is necessary, or we'd reach AtCleanup_Portals with the cleanup hook
* still unexecuted.
*/
if (PointerIsValid(portal->cleanup))
{
portal->cleanup(portal);
portal->cleanup = NULL;
}
}
/*
* PortalDrop
* Destroy the portal.
*/
void
PortalDrop(Portal portal, bool isTopCommit)
{
AssertArg(PortalIsValid(portal));
/*
* Don't allow dropping a pinned portal, it's still needed by whoever
* pinned it.
*/
if (portal->portalPinned)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cannot drop pinned portal \"%s\"", portal->name)));
/*
* Not sure if the PORTAL_ACTIVE case can validly happen or not...
*/
if (portal->status == PORTAL_ACTIVE)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cannot drop active portal \"%s\"", portal->name)));
/*
* Allow portalcmds.c to clean up the state it knows about, in particular
* shutting down the executor if still active. This step potentially runs
* user-defined code so failure has to be expected. It's the cleanup
* hook's responsibility to not try to do that more than once, in the case
* that failure occurs and then we come back to drop the portal again
* during transaction abort.
*
* Note: in most paths of control, this will have been done already in
* MarkPortalDone or MarkPortalFailed. We're just making sure.
*/
if (PointerIsValid(portal->cleanup))
{
portal->cleanup(portal);
portal->cleanup = NULL;
}
/*
* Remove portal from hash table. Because we do this here, we will not
* come back to try to remove the portal again if there's any error in the
* subsequent steps. Better to leak a little memory than to get into an
* infinite error-recovery loop.
*/
PortalHashTableDelete(portal);
/* drop cached plan reference, if any */
PortalReleaseCachedPlan(portal);
/*
* If portal has a snapshot protecting its data, release that. This needs
* a little care since the registration will be attached to the portal's
* resowner; if the portal failed, we will already have released the
* resowner (and the snapshot) during transaction abort.
*/
if (portal->holdSnapshot)
{
if (portal->resowner)
UnregisterSnapshotFromOwner(portal->holdSnapshot,
portal->resowner);
portal->holdSnapshot = NULL;
}
/*
* Release any resources still attached to the portal. There are several
* cases being covered here:
*
* Top transaction commit (indicated by isTopCommit): normally we should
* do nothing here and let the regular end-of-transaction resource
* releasing mechanism handle these resources too. However, if we have a
* FAILED portal (eg, a cursor that got an error), we'd better clean up
* its resources to avoid resource-leakage warning messages.
*
* Sub transaction commit: never comes here at all, since we don't kill
* any portals in AtSubCommit_Portals().
*
* Main or sub transaction abort: we will do nothing here because
* portal->resowner was already set NULL; the resources were already
* cleaned up in transaction abort.
*
* Ordinary portal drop: must release resources. However, if the portal
* is not FAILED then we do not release its locks. The locks become the
* responsibility of the transaction's ResourceOwner (since it is the
* parent of the portal's owner) and will be released when the transaction
* eventually ends.
*/
if (portal->resowner &&
(!isTopCommit || portal->status == PORTAL_FAILED))
{
bool isCommit = (portal->status != PORTAL_FAILED);
ResourceOwnerRelease(portal->resowner,
RESOURCE_RELEASE_BEFORE_LOCKS,
isCommit, false);
ResourceOwnerRelease(portal->resowner,
RESOURCE_RELEASE_LOCKS,
isCommit, false);
ResourceOwnerRelease(portal->resowner,
RESOURCE_RELEASE_AFTER_LOCKS,
isCommit, false);
ResourceOwnerDelete(portal->resowner);
}
portal->resowner = NULL;
/*
* Delete tuplestore if present. We should do this even under error
* conditions; since the tuplestore would have been using cross-
* transaction storage, its temp files need to be explicitly deleted.
*/
if (portal->holdStore)
{
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(portal->holdContext);
tuplestore_end(portal->holdStore);
MemoryContextSwitchTo(oldcontext);
portal->holdStore = NULL;
}
/* delete tuplestore storage, if any */
if (portal->holdContext)
MemoryContextDelete(portal->holdContext);
/* release subsidiary storage */
MemoryContextDelete(portal->portalContext);
/* release portal struct (it's in TopPortalContext) */
pfree(portal);
}
/*
* Delete all declared cursors.
*
* Used by commands: CLOSE ALL, DISCARD ALL
*/
void
PortalHashTableDeleteAll(void)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
if (PortalHashTable == NULL)
return;
hash_seq_init(&status, PortalHashTable);
while ((hentry = hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
/* Can't close the active portal (the one running the command) */
if (portal->status == PORTAL_ACTIVE)
continue;
PortalDrop(portal, false);
/* Restart the iteration in case that led to other drops */
hash_seq_term(&status);
hash_seq_init(&status, PortalHashTable);
}
}
/*
* "Hold" a portal. Prepare it for access by later transactions.
*/
static void
HoldPortal(Portal portal)
{
/*
* Note that PersistHoldablePortal() must release all resources used by
* the portal that are local to the creating transaction.
*/
PortalCreateHoldStore(portal);
PersistHoldablePortal(portal);
/* drop cached plan reference, if any */
PortalReleaseCachedPlan(portal);
/*
* Any resources belonging to the portal will be released in the upcoming
* transaction-wide cleanup; the portal will no longer have its own
* resources.
*/
portal->resowner = NULL;
/*
* Having successfully exported the holdable cursor, mark it as not
* belonging to this transaction.
*/
portal->createSubid = InvalidSubTransactionId;
portal->activeSubid = InvalidSubTransactionId;
}
/*
* Pre-commit processing for portals.
*
* Holdable cursors created in this transaction need to be converted to
* materialized form, since we are going to close down the executor and
* release locks. Non-holdable portals created in this transaction are
* simply removed. Portals remaining from prior transactions should be
* left untouched.
*
* Returns true if any portals changed state (possibly causing user-defined
* code to be run), false if not.
*/
bool
PreCommit_Portals(bool isPrepare)
{
bool result = false;
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
/*
* There should be no pinned portals anymore. Complain if someone
* leaked one. Auto-held portals are allowed; we assume that whoever
* pinned them is managing them.
*/
if (portal->portalPinned && !portal->autoHeld)
elog(ERROR, "cannot commit while a portal is pinned");
/*
* Do not touch active portals --- this can only happen in the case of
* a multi-transaction utility command, such as VACUUM.
*
* Note however that any resource owner attached to such a portal is
* still going to go away, so don't leave a dangling pointer.
*/
if (portal->status == PORTAL_ACTIVE)
{
portal->resowner = NULL;
continue;
}
/* Is it a holdable portal created in the current xact? */
if ((portal->cursorOptions & CURSOR_OPT_HOLD) &&
portal->createSubid != InvalidSubTransactionId &&
portal->status == PORTAL_READY)
{
/*
* We are exiting the transaction that created a holdable cursor.
* Instead of dropping the portal, prepare it for access by later
* transactions.
*
* However, if this is PREPARE TRANSACTION rather than COMMIT,
* refuse PREPARE, because the semantics seem pretty unclear.
*/
if (isPrepare)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE a transaction that has created a cursor WITH HOLD")));
HoldPortal(portal);
/* Report we changed state */
result = true;
}
else if (portal->createSubid == InvalidSubTransactionId)
{
/*
* Do nothing to cursors held over from a previous transaction
* (including ones we just froze in a previous cycle of this loop)
*/
continue;
}
else
{
/* Zap all non-holdable portals */
PortalDrop(portal, true);
/* Report we changed state */
result = true;
}
/*
* After either freezing or dropping a portal, we have to restart the
* iteration, because we could have invoked user-defined code that
* caused a drop of the next portal in the hash chain.
*/
hash_seq_term(&status);
hash_seq_init(&status, PortalHashTable);
}
return result;
}
/*
* Abort processing for portals.
*
* At this point we run the cleanup hook if present, but we can't release the
* portal's memory until the cleanup call.
*/
void
AtAbort_Portals(void)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
/*
* When elog(FATAL) is progress, we need to set the active portal to
* failed, so that PortalCleanup() doesn't run the executor shutdown.
*/
if (portal->status == PORTAL_ACTIVE && shmem_exit_inprogress)
MarkPortalFailed(portal);
/*
* Do nothing else to cursors held over from a previous transaction.
*/
if (portal->createSubid == InvalidSubTransactionId)
continue;
/*
* Do nothing to auto-held cursors. This is similar to the case of a
* cursor from a previous transaction, but it could also be that the
* cursor was auto-held in this transaction, so it wants to live on.
*/
if (portal->autoHeld)
continue;
/*
* If it was created in the current transaction, we can't do normal
* shutdown on a READY portal either; it might refer to objects
* created in the failed transaction. See comments in
* AtSubAbort_Portals.
*/
if (portal->status == PORTAL_READY)
MarkPortalFailed(portal);
/*
* Allow portalcmds.c to clean up the state it knows about, if we
* haven't already.
*/
if (PointerIsValid(portal->cleanup))
{
portal->cleanup(portal);
portal->cleanup = NULL;
}
/* drop cached plan reference, if any */
PortalReleaseCachedPlan(portal);
/*
* Any resources belonging to the portal will be released in the
* upcoming transaction-wide cleanup; they will be gone before we run
* PortalDrop.
*/
portal->resowner = NULL;
/*
* Although we can't delete the portal data structure proper, we can
* release any memory in subsidiary contexts, such as executor state.
* The cleanup hook was the last thing that might have needed data
* there. But leave active portals alone.
*/
if (portal->status != PORTAL_ACTIVE)
MemoryContextDeleteChildren(portal->portalContext);
}
}
/*
* Post-abort cleanup for portals.
*
* Delete all portals not held over from prior transactions. */
void
AtCleanup_Portals(void)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
/*
* Do not touch active portals --- this can only happen in the case of
* a multi-transaction command.
*/
if (portal->status == PORTAL_ACTIVE)
continue;
/*
* Do nothing to cursors held over from a previous transaction or
* auto-held ones.
*/
if (portal->createSubid == InvalidSubTransactionId || portal->autoHeld)
{
Assert(portal->status != PORTAL_ACTIVE);
Assert(portal->resowner == NULL);
continue;
}
/*
* If a portal is still pinned, forcibly unpin it. PortalDrop will not
* let us drop the portal otherwise. Whoever pinned the portal was
* interrupted by the abort too and won't try to use it anymore.
*/
if (portal->portalPinned)
portal->portalPinned = false;
/*
* We had better not call any user-defined code during cleanup, so if
* the cleanup hook hasn't been run yet, too bad; we'll just skip it.
*/
if (PointerIsValid(portal->cleanup))
{
elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
portal->cleanup = NULL;
}
/* Zap it. */
PortalDrop(portal, false);
}
}
/*
* Portal-related cleanup when we return to the main loop on error.
*
* This is different from the cleanup at transaction abort. Auto-held portals
* are cleaned up on error but not on transaction abort.
*/
void
PortalErrorCleanup(void)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
if (portal->autoHeld)
{
portal->portalPinned = false;
PortalDrop(portal, false);
}
}
}
/*
* Pre-subcommit processing for portals.
*
* Reassign portals created or used in the current subtransaction to the
* parent subtransaction.
*/
void
AtSubCommit_Portals(SubTransactionId mySubid,
SubTransactionId parentSubid,
ResourceOwner parentXactOwner)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
if (portal->createSubid == mySubid)
{
portal->createSubid = parentSubid;
if (portal->resowner)
ResourceOwnerNewParent(portal->resowner, parentXactOwner);
}
if (portal->activeSubid == mySubid)
portal->activeSubid = parentSubid;
}
}
/*
* Subtransaction abort handling for portals.
*
* Deactivate portals created or used during the failed subtransaction.
* Note that per AtSubCommit_Portals, this will catch portals created/used
* in descendants of the subtransaction too.
*
* We don't destroy any portals here; that's done in AtSubCleanup_Portals.
*/
void
AtSubAbort_Portals(SubTransactionId mySubid,
SubTransactionId parentSubid,
ResourceOwner myXactOwner,
ResourceOwner parentXactOwner)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
/* Was it created in this subtransaction? */
if (portal->createSubid != mySubid)
{
/* No, but maybe it was used in this subtransaction? */
if (portal->activeSubid == mySubid)
{
/* Maintain activeSubid until the portal is removed */
portal->activeSubid = parentSubid;
/*
* A MarkPortalActive() caller ran an upper-level portal in
* this subtransaction and left the portal ACTIVE. This can't
* happen, but force the portal into FAILED state for the same
* reasons discussed below.
*
* We assume we can get away without forcing upper-level READY
* portals to fail, even if they were run and then suspended.
* In theory a suspended upper-level portal could have
* acquired some references to objects that are about to be
* destroyed, but there should be sufficient defenses against
* such cases: the portal's original query cannot contain such
* references, and any references within, say, cached plans of
* PL/pgSQL functions are not from active queries and should
* be protected by revalidation logic.
*/
if (portal->status == PORTAL_ACTIVE)
MarkPortalFailed(portal);
/*
* Also, if we failed it during the current subtransaction
* (either just above, or earlier), reattach its resource
* owner to the current subtransaction's resource owner, so
* that any resources it still holds will be released while
* cleaning up this subtransaction. This prevents some corner
* cases wherein we might get Asserts or worse while cleaning
* up objects created during the current subtransaction
* (because they're still referenced within this portal).
*/
if (portal->status == PORTAL_FAILED && portal->resowner)
{
ResourceOwnerNewParent(portal->resowner, myXactOwner);
portal->resowner = NULL;
}
}
/* Done if it wasn't created in this subtransaction */
continue;
}
/*
* Force any live portals of my own subtransaction into FAILED state.
* We have to do this because they might refer to objects created or
* changed in the failed subtransaction, leading to crashes within
* ExecutorEnd when portalcmds.c tries to close down the portal.
* Currently, every MarkPortalActive() caller ensures it updates the
* portal status again before relinquishing control, so ACTIVE can't
* happen here. If it does happen, dispose the portal like existing
* MarkPortalActive() callers would.
*/
if (portal->status == PORTAL_READY ||
portal->status == PORTAL_ACTIVE)
MarkPortalFailed(portal);
/*
* Allow portalcmds.c to clean up the state it knows about, if we
* haven't already.
*/
if (PointerIsValid(portal->cleanup))
{
portal->cleanup(portal);
portal->cleanup = NULL;
}
/* drop cached plan reference, if any */
PortalReleaseCachedPlan(portal);
/*
* Any resources belonging to the portal will be released in the
* upcoming transaction-wide cleanup; they will be gone before we run
* PortalDrop.
*/
portal->resowner = NULL;
/*
* Although we can't delete the portal data structure proper, we can
* release any memory in subsidiary contexts, such as executor state.
* The cleanup hook was the last thing that might have needed data
* there.
*/
MemoryContextDeleteChildren(portal->portalContext);
}
}
/*
* Post-subabort cleanup for portals.
*
* Drop all portals created in the failed subtransaction (but note that
* we will not drop any that were reassigned to the parent above).
*/
void
AtSubCleanup_Portals(SubTransactionId mySubid)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
if (portal->createSubid != mySubid)
continue;
/*
* If a portal is still pinned, forcibly unpin it. PortalDrop will not
* let us drop the portal otherwise. Whoever pinned the portal was
* interrupted by the abort too and won't try to use it anymore.
*/
if (portal->portalPinned)
portal->portalPinned = false;
/*
* We had better not call any user-defined code during cleanup, so if
* the cleanup hook hasn't been run yet, too bad; we'll just skip it.
*/
if (PointerIsValid(portal->cleanup))
{
elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
portal->cleanup = NULL;
}
/* Zap it. */
PortalDrop(portal, false);
}
}
/* Find all available cursors */
Datum
pg_cursor(PG_FUNCTION_ARGS)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
MemoryContext per_query_ctx;
MemoryContext oldcontext;
HASH_SEQ_STATUS hash_seq;
PortalHashEnt *hentry;
/* check to see if caller supports us returning a tuplestore */
if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("set-valued function called in context that cannot accept a set")));
if (!(rsinfo->allowedModes & SFRM_Materialize))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("materialize mode required, but it is not " \
"allowed in this context")));
/* need to build tuplestore in query context */
per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
oldcontext = MemoryContextSwitchTo(per_query_ctx);
/*
* build tupdesc for result tuples. This must match the definition of the
* pg_cursors view in system_views.sql
*/
tupdesc = CreateTemplateTupleDesc(6, false);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "statement",
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_holdable",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_binary",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 5, "is_scrollable",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 6, "creation_time",
TIMESTAMPTZOID, -1, 0);
/*
* We put all the tuples into a tuplestore in one scan of the hashtable.
* This avoids any issue of the hashtable possibly changing between calls.
*/
tupstore =
tuplestore_begin_heap(rsinfo->allowedModes & SFRM_Materialize_Random,
false, work_mem);
/* generate junk in short-term context */
MemoryContextSwitchTo(oldcontext);
hash_seq_init(&hash_seq, PortalHashTable);
while ((hentry = hash_seq_search(&hash_seq)) != NULL)
{
Portal portal = hentry->portal;
Datum values[6];
bool nulls[6];
/* report only "visible" entries */
if (!portal->visible)
continue;
MemSet(nulls, 0, sizeof(nulls));
values[0] = CStringGetTextDatum(portal->name);
values[1] = CStringGetTextDatum(portal->sourceText);
values[2] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_HOLD);
values[3] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_BINARY);
values[4] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_SCROLL);
values[5] = TimestampTzGetDatum(portal->creation_time);
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
}
/* clean up and return the tuplestore */
tuplestore_donestoring(tupstore);
rsinfo->returnMode = SFRM_Materialize;
rsinfo->setResult = tupstore;
rsinfo->setDesc = tupdesc;
return (Datum) 0;
}
bool
ThereAreNoReadyPortals(void)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
if (portal->status == PORTAL_READY)
return false;
}
return true;
}
/*
* Hold all pinned portals.
*
* A procedural language implementation that uses pinned portals for its
* internally generated cursors can call this in its COMMIT command to convert
* those cursors to held cursors, so that they survive the transaction end.
* We mark those portals as "auto-held" so that exception exit knows to clean
* them up. (In normal, non-exception code paths, the PL needs to clean those
* portals itself, since transaction end won't do it anymore, but that should
* be normal practice anyway.)
*/
void
HoldPinnedPortals(void)
{
HASH_SEQ_STATUS status;
PortalHashEnt *hentry;
hash_seq_init(&status, PortalHashTable);
while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
{
Portal portal = hentry->portal;
if (portal->portalPinned && !portal->autoHeld)
{
/*
* Doing transaction control, especially abort, inside a cursor
* loop that is not read-only, for example using UPDATE ...
* RETURNING, has weird semantics issues. Also, this
* implementation wouldn't work, because such portals cannot be
* held. (The core grammar enforces that only SELECT statements
* can drive a cursor, but for example PL/pgSQL does not restrict
* it.)
*/
if (portal->strategy != PORTAL_ONE_SELECT)
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_TERMINATION),
errmsg("cannot perform transaction commands inside a cursor loop that is not read-only")));
portal->autoHeld = true;
HoldPortal(portal);
}
}
}