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event_trigger.c
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/*-------------------------------------------------------------------------
*
* event_trigger.c
* PostgreSQL EVENT TRIGGER support code.
*
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/commands/event_trigger.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_database.h"
#include "catalog/pg_event_trigger.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_opfamily.h"
#include "catalog/pg_parameter_acl.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_ts_config.h"
#include "catalog/pg_type.h"
#include "commands/event_trigger.h"
#include "commands/extension.h"
#include "commands/trigger.h"
#include "funcapi.h"
#include "lib/ilist.h"
#include "miscadmin.h"
#include "parser/parse_func.h"
#include "pgstat.h"
#include "storage/lmgr.h"
#include "tcop/deparse_utility.h"
#include "tcop/utility.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/evtcache.h"
#include "utils/fmgroids.h"
#include "utils/fmgrprotos.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
typedef struct EventTriggerQueryState
{
/* memory context for this state's objects */
MemoryContext cxt;
/* sql_drop */
slist_head SQLDropList;
bool in_sql_drop;
/* table_rewrite */
Oid table_rewrite_oid; /* InvalidOid, or set for table_rewrite
* event */
int table_rewrite_reason; /* AT_REWRITE reason */
/* Support for command collection */
bool commandCollectionInhibited;
CollectedCommand *currentCommand;
List *commandList; /* list of CollectedCommand; see
* deparse_utility.h */
struct EventTriggerQueryState *previous;
} EventTriggerQueryState;
static EventTriggerQueryState *currentEventTriggerState = NULL;
/* GUC parameter */
bool event_triggers = true;
/* Support for dropped objects */
typedef struct SQLDropObject
{
ObjectAddress address;
const char *schemaname;
const char *objname;
const char *objidentity;
const char *objecttype;
List *addrnames;
List *addrargs;
bool original;
bool normal;
bool istemp;
slist_node next;
} SQLDropObject;
static void AlterEventTriggerOwner_internal(Relation rel,
HeapTuple tup,
Oid newOwnerId);
static void error_duplicate_filter_variable(const char *defname);
static Datum filter_list_to_array(List *filterlist);
static Oid insert_event_trigger_tuple(const char *trigname, const char *eventname,
Oid evtOwner, Oid funcoid, List *taglist);
static void validate_ddl_tags(const char *filtervar, List *taglist);
static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
static const char *stringify_grant_objtype(ObjectType objtype);
static const char *stringify_adefprivs_objtype(ObjectType objtype);
static void SetDatabaseHasLoginEventTriggers(void);
/*
* Create an event trigger.
*/
Oid
CreateEventTrigger(CreateEventTrigStmt *stmt)
{
HeapTuple tuple;
Oid funcoid;
Oid funcrettype;
Oid evtowner = GetUserId();
ListCell *lc;
List *tags = NULL;
/*
* It would be nice to allow database owners or even regular users to do
* this, but there are obvious privilege escalation risks which would have
* to somehow be plugged first.
*/
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied to create event trigger \"%s\"",
stmt->trigname),
errhint("Must be superuser to create an event trigger.")));
/* Validate event name. */
if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
strcmp(stmt->eventname, "ddl_command_end") != 0 &&
strcmp(stmt->eventname, "sql_drop") != 0 &&
strcmp(stmt->eventname, "login") != 0 &&
strcmp(stmt->eventname, "table_rewrite") != 0)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("unrecognized event name \"%s\"",
stmt->eventname)));
/* Validate filter conditions. */
foreach(lc, stmt->whenclause)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "tag") == 0)
{
if (tags != NULL)
error_duplicate_filter_variable(def->defname);
tags = (List *) def->arg;
}
else
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("unrecognized filter variable \"%s\"", def->defname)));
}
/* Validate tag list, if any. */
if ((strcmp(stmt->eventname, "ddl_command_start") == 0 ||
strcmp(stmt->eventname, "ddl_command_end") == 0 ||
strcmp(stmt->eventname, "sql_drop") == 0)
&& tags != NULL)
validate_ddl_tags("tag", tags);
else if (strcmp(stmt->eventname, "table_rewrite") == 0
&& tags != NULL)
validate_table_rewrite_tags("tag", tags);
else if (strcmp(stmt->eventname, "login") == 0 && tags != NULL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("tag filtering is not supported for login event triggers")));
/*
* Give user a nice error message if an event trigger of the same name
* already exists.
*/
tuple = SearchSysCache1(EVENTTRIGGERNAME, CStringGetDatum(stmt->trigname));
if (HeapTupleIsValid(tuple))
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("event trigger \"%s\" already exists",
stmt->trigname)));
/* Find and validate the trigger function. */
funcoid = LookupFuncName(stmt->funcname, 0, NULL, false);
funcrettype = get_func_rettype(funcoid);
if (funcrettype != EVENT_TRIGGEROID)
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("function %s must return type %s",
NameListToString(stmt->funcname), "event_trigger")));
/* Insert catalog entries. */
return insert_event_trigger_tuple(stmt->trigname, stmt->eventname,
evtowner, funcoid, tags);
}
/*
* Validate DDL command tags.
*/
static void
validate_ddl_tags(const char *filtervar, List *taglist)
{
ListCell *lc;
foreach(lc, taglist)
{
const char *tagstr = strVal(lfirst(lc));
CommandTag commandTag = GetCommandTagEnum(tagstr);
if (commandTag == CMDTAG_UNKNOWN)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("filter value \"%s\" not recognized for filter variable \"%s\"",
tagstr, filtervar)));
if (!command_tag_event_trigger_ok(commandTag))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s represents an SQL statement name */
errmsg("event triggers are not supported for %s",
tagstr)));
}
}
/*
* Validate DDL command tags for event table_rewrite.
*/
static void
validate_table_rewrite_tags(const char *filtervar, List *taglist)
{
ListCell *lc;
foreach(lc, taglist)
{
const char *tagstr = strVal(lfirst(lc));
CommandTag commandTag = GetCommandTagEnum(tagstr);
if (!command_tag_table_rewrite_ok(commandTag))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s represents an SQL statement name */
errmsg("event triggers are not supported for %s",
tagstr)));
}
}
/*
* Complain about a duplicate filter variable.
*/
static void
error_duplicate_filter_variable(const char *defname)
{
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("filter variable \"%s\" specified more than once",
defname)));
}
/*
* Insert the new pg_event_trigger row and record dependencies.
*/
static Oid
insert_event_trigger_tuple(const char *trigname, const char *eventname, Oid evtOwner,
Oid funcoid, List *taglist)
{
Relation tgrel;
Oid trigoid;
HeapTuple tuple;
Datum values[Natts_pg_trigger];
bool nulls[Natts_pg_trigger];
NameData evtnamedata,
evteventdata;
ObjectAddress myself,
referenced;
/* Open pg_event_trigger. */
tgrel = table_open(EventTriggerRelationId, RowExclusiveLock);
/* Build the new pg_trigger tuple. */
trigoid = GetNewOidWithIndex(tgrel, EventTriggerOidIndexId,
Anum_pg_event_trigger_oid);
values[Anum_pg_event_trigger_oid - 1] = ObjectIdGetDatum(trigoid);
memset(nulls, false, sizeof(nulls));
namestrcpy(&evtnamedata, trigname);
values[Anum_pg_event_trigger_evtname - 1] = NameGetDatum(&evtnamedata);
namestrcpy(&evteventdata, eventname);
values[Anum_pg_event_trigger_evtevent - 1] = NameGetDatum(&evteventdata);
values[Anum_pg_event_trigger_evtowner - 1] = ObjectIdGetDatum(evtOwner);
values[Anum_pg_event_trigger_evtfoid - 1] = ObjectIdGetDatum(funcoid);
values[Anum_pg_event_trigger_evtenabled - 1] =
CharGetDatum(TRIGGER_FIRES_ON_ORIGIN);
if (taglist == NIL)
nulls[Anum_pg_event_trigger_evttags - 1] = true;
else
values[Anum_pg_event_trigger_evttags - 1] =
filter_list_to_array(taglist);
/* Insert heap tuple. */
tuple = heap_form_tuple(tgrel->rd_att, values, nulls);
CatalogTupleInsert(tgrel, tuple);
heap_freetuple(tuple);
/*
* Login event triggers have an additional flag in pg_database to enable
* faster lookups in hot codepaths. Set the flag unless already True.
*/
if (strcmp(eventname, "login") == 0)
SetDatabaseHasLoginEventTriggers();
/* Depend on owner. */
recordDependencyOnOwner(EventTriggerRelationId, trigoid, evtOwner);
/* Depend on event trigger function. */
myself.classId = EventTriggerRelationId;
myself.objectId = trigoid;
myself.objectSubId = 0;
referenced.classId = ProcedureRelationId;
referenced.objectId = funcoid;
referenced.objectSubId = 0;
recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
/* Depend on extension, if any. */
recordDependencyOnCurrentExtension(&myself, false);
/* Post creation hook for new event trigger */
InvokeObjectPostCreateHook(EventTriggerRelationId, trigoid, 0);
/* Close pg_event_trigger. */
table_close(tgrel, RowExclusiveLock);
return trigoid;
}
/*
* In the parser, a clause like WHEN tag IN ('cmd1', 'cmd2') is represented
* by a DefElem whose value is a List of String nodes; in the catalog, we
* store the list of strings as a text array. This function transforms the
* former representation into the latter one.
*
* For cleanliness, we store command tags in the catalog as text. It's
* possible (although not currently anticipated) that we might have
* a case-sensitive filter variable in the future, in which case this would
* need some further adjustment.
*/
static Datum
filter_list_to_array(List *filterlist)
{
ListCell *lc;
Datum *data;
int i = 0,
l = list_length(filterlist);
data = (Datum *) palloc(l * sizeof(Datum));
foreach(lc, filterlist)
{
const char *value = strVal(lfirst(lc));
char *result,
*p;
result = pstrdup(value);
for (p = result; *p; p++)
*p = pg_ascii_toupper((unsigned char) *p);
data[i++] = PointerGetDatum(cstring_to_text(result));
pfree(result);
}
return PointerGetDatum(construct_array_builtin(data, l, TEXTOID));
}
/*
* Set pg_database.dathasloginevt flag for current database indicating that
* current database has on login event triggers.
*/
void
SetDatabaseHasLoginEventTriggers(void)
{
/* Set dathasloginevt flag in pg_database */
Form_pg_database db;
Relation pg_db = table_open(DatabaseRelationId, RowExclusiveLock);
ItemPointerData otid;
HeapTuple tuple;
/*
* Use shared lock to prevent a conflict with EventTriggerOnLogin() trying
* to reset pg_database.dathasloginevt flag. Note, this lock doesn't
* effectively blocks database or other objection. It's just custom lock
* tag used to prevent multiple backends changing
* pg_database.dathasloginevt flag.
*/
LockSharedObject(DatabaseRelationId, MyDatabaseId, 0, AccessExclusiveLock);
tuple = SearchSysCacheLockedCopy1(DATABASEOID, ObjectIdGetDatum(MyDatabaseId));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for database %u", MyDatabaseId);
otid = tuple->t_self;
db = (Form_pg_database) GETSTRUCT(tuple);
if (!db->dathasloginevt)
{
db->dathasloginevt = true;
CatalogTupleUpdate(pg_db, &otid, tuple);
CommandCounterIncrement();
}
UnlockTuple(pg_db, &otid, InplaceUpdateTupleLock);
table_close(pg_db, RowExclusiveLock);
heap_freetuple(tuple);
}
/*
* ALTER EVENT TRIGGER foo ENABLE|DISABLE|ENABLE ALWAYS|REPLICA
*/
Oid
AlterEventTrigger(AlterEventTrigStmt *stmt)
{
Relation tgrel;
HeapTuple tup;
Oid trigoid;
Form_pg_event_trigger evtForm;
char tgenabled = stmt->tgenabled;
tgrel = table_open(EventTriggerRelationId, RowExclusiveLock);
tup = SearchSysCacheCopy1(EVENTTRIGGERNAME,
CStringGetDatum(stmt->trigname));
if (!HeapTupleIsValid(tup))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("event trigger \"%s\" does not exist",
stmt->trigname)));
evtForm = (Form_pg_event_trigger) GETSTRUCT(tup);
trigoid = evtForm->oid;
if (!object_ownercheck(EventTriggerRelationId, trigoid, GetUserId()))
aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_EVENT_TRIGGER,
stmt->trigname);
/* tuple is a copy, so we can modify it below */
evtForm->evtenabled = tgenabled;
CatalogTupleUpdate(tgrel, &tup->t_self, tup);
/*
* Login event triggers have an additional flag in pg_database to enable
* faster lookups in hot codepaths. Set the flag unless already True.
*/
if (namestrcmp(&evtForm->evtevent, "login") == 0 &&
tgenabled != TRIGGER_DISABLED)
SetDatabaseHasLoginEventTriggers();
InvokeObjectPostAlterHook(EventTriggerRelationId,
trigoid, 0);
/* clean up */
heap_freetuple(tup);
table_close(tgrel, RowExclusiveLock);
return trigoid;
}
/*
* Change event trigger's owner -- by name
*/
ObjectAddress
AlterEventTriggerOwner(const char *name, Oid newOwnerId)
{
Oid evtOid;
HeapTuple tup;
Form_pg_event_trigger evtForm;
Relation rel;
ObjectAddress address;
rel = table_open(EventTriggerRelationId, RowExclusiveLock);
tup = SearchSysCacheCopy1(EVENTTRIGGERNAME, CStringGetDatum(name));
if (!HeapTupleIsValid(tup))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("event trigger \"%s\" does not exist", name)));
evtForm = (Form_pg_event_trigger) GETSTRUCT(tup);
evtOid = evtForm->oid;
AlterEventTriggerOwner_internal(rel, tup, newOwnerId);
ObjectAddressSet(address, EventTriggerRelationId, evtOid);
heap_freetuple(tup);
table_close(rel, RowExclusiveLock);
return address;
}
/*
* Change event trigger owner, by OID
*/
void
AlterEventTriggerOwner_oid(Oid trigOid, Oid newOwnerId)
{
HeapTuple tup;
Relation rel;
rel = table_open(EventTriggerRelationId, RowExclusiveLock);
tup = SearchSysCacheCopy1(EVENTTRIGGEROID, ObjectIdGetDatum(trigOid));
if (!HeapTupleIsValid(tup))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("event trigger with OID %u does not exist", trigOid)));
AlterEventTriggerOwner_internal(rel, tup, newOwnerId);
heap_freetuple(tup);
table_close(rel, RowExclusiveLock);
}
/*
* Internal workhorse for changing an event trigger's owner
*/
static void
AlterEventTriggerOwner_internal(Relation rel, HeapTuple tup, Oid newOwnerId)
{
Form_pg_event_trigger form;
form = (Form_pg_event_trigger) GETSTRUCT(tup);
if (form->evtowner == newOwnerId)
return;
if (!object_ownercheck(EventTriggerRelationId, form->oid, GetUserId()))
aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_EVENT_TRIGGER,
NameStr(form->evtname));
/* New owner must be a superuser */
if (!superuser_arg(newOwnerId))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied to change owner of event trigger \"%s\"",
NameStr(form->evtname)),
errhint("The owner of an event trigger must be a superuser.")));
form->evtowner = newOwnerId;
CatalogTupleUpdate(rel, &tup->t_self, tup);
/* Update owner dependency reference */
changeDependencyOnOwner(EventTriggerRelationId,
form->oid,
newOwnerId);
InvokeObjectPostAlterHook(EventTriggerRelationId,
form->oid, 0);
}
/*
* get_event_trigger_oid - Look up an event trigger by name to find its OID.
*
* If missing_ok is false, throw an error if trigger not found. If
* true, just return InvalidOid.
*/
Oid
get_event_trigger_oid(const char *trigname, bool missing_ok)
{
Oid oid;
oid = GetSysCacheOid1(EVENTTRIGGERNAME, Anum_pg_event_trigger_oid,
CStringGetDatum(trigname));
if (!OidIsValid(oid) && !missing_ok)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("event trigger \"%s\" does not exist", trigname)));
return oid;
}
/*
* Return true when we want to fire given Event Trigger and false otherwise,
* filtering on the session replication role and the event trigger registered
* tags matching.
*/
static bool
filter_event_trigger(CommandTag tag, EventTriggerCacheItem *item)
{
/*
* Filter by session replication role, knowing that we never see disabled
* items down here.
*/
if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
{
if (item->enabled == TRIGGER_FIRES_ON_ORIGIN)
return false;
}
else
{
if (item->enabled == TRIGGER_FIRES_ON_REPLICA)
return false;
}
/* Filter by tags, if any were specified. */
if (!bms_is_empty(item->tagset) && !bms_is_member(tag, item->tagset))
return false;
/* if we reach that point, we're not filtering out this item */
return true;
}
static CommandTag
EventTriggerGetTag(Node *parsetree, EventTriggerEvent event)
{
if (event == EVT_Login)
return CMDTAG_LOGIN;
else
return CreateCommandTag(parsetree);
}
/*
* Setup for running triggers for the given event. Return value is an OID list
* of functions to run; if there are any, trigdata is filled with an
* appropriate EventTriggerData for them to receive.
*/
static List *
EventTriggerCommonSetup(Node *parsetree,
EventTriggerEvent event, const char *eventstr,
EventTriggerData *trigdata, bool unfiltered)
{
CommandTag tag;
List *cachelist;
ListCell *lc;
List *runlist = NIL;
/*
* We want the list of command tags for which this procedure is actually
* invoked to match up exactly with the list that CREATE EVENT TRIGGER
* accepts. This debugging cross-check will throw an error if this
* function is invoked for a command tag that CREATE EVENT TRIGGER won't
* accept. (Unfortunately, there doesn't seem to be any simple, automated
* way to verify that CREATE EVENT TRIGGER doesn't accept extra stuff that
* never reaches this control point.)
*
* If this cross-check fails for you, you probably need to either adjust
* standard_ProcessUtility() not to invoke event triggers for the command
* type in question, or you need to adjust event_trigger_ok to accept the
* relevant command tag.
*/
#ifdef USE_ASSERT_CHECKING
{
CommandTag dbgtag;
dbgtag = EventTriggerGetTag(parsetree, event);
if (event == EVT_DDLCommandStart ||
event == EVT_DDLCommandEnd ||
event == EVT_SQLDrop ||
event == EVT_Login)
{
if (!command_tag_event_trigger_ok(dbgtag))
elog(ERROR, "unexpected command tag \"%s\"", GetCommandTagName(dbgtag));
}
else if (event == EVT_TableRewrite)
{
if (!command_tag_table_rewrite_ok(dbgtag))
elog(ERROR, "unexpected command tag \"%s\"", GetCommandTagName(dbgtag));
}
}
#endif
/* Use cache to find triggers for this event; fast exit if none. */
cachelist = EventCacheLookup(event);
if (cachelist == NIL)
return NIL;
/* Get the command tag. */
tag = EventTriggerGetTag(parsetree, event);
/*
* Filter list of event triggers by command tag, and copy them into our
* memory context. Once we start running the command triggers, or indeed
* once we do anything at all that touches the catalogs, an invalidation
* might leave cachelist pointing at garbage, so we must do this before we
* can do much else.
*/
foreach(lc, cachelist)
{
EventTriggerCacheItem *item = lfirst(lc);
if (unfiltered || filter_event_trigger(tag, item))
{
/* We must plan to fire this trigger. */
runlist = lappend_oid(runlist, item->fnoid);
}
}
/* Don't spend any more time on this if no functions to run */
if (runlist == NIL)
return NIL;
trigdata->type = T_EventTriggerData;
trigdata->event = eventstr;
trigdata->parsetree = parsetree;
trigdata->tag = tag;
return runlist;
}
/*
* Fire ddl_command_start triggers.
*/
void
EventTriggerDDLCommandStart(Node *parsetree)
{
List *runlist;
EventTriggerData trigdata;
#if !defined(__EMSCRIPTEN__) && !defined(__wasi__)
/*
* Event Triggers are completely disabled in standalone mode. There are
* (at least) two reasons for this:
*
* 1. A sufficiently broken event trigger might not only render the
* database unusable, but prevent disabling itself to fix the situation.
* In this scenario, restarting in standalone mode provides an escape
* hatch.
*
* 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
* therefore will malfunction if pg_event_trigger's indexes are damaged.
* To allow recovery from a damaged index, we need some operating mode
* wherein event triggers are disabled. (Or we could implement
* heapscan-and-sort logic for that case, but having disaster recovery
* scenarios depend on code that's otherwise untested isn't appetizing.)
*
* Additionally, event triggers can be disabled with a superuser-only GUC
* to make fixing database easier as per 1 above.
*/
if (!IsUnderPostmaster || !event_triggers)
return;
#else
if (!event_triggers)
return;
#endif
runlist = EventTriggerCommonSetup(parsetree,
EVT_DDLCommandStart,
"ddl_command_start",
&trigdata, false);
if (runlist == NIL)
return;
/* Run the triggers. */
EventTriggerInvoke(runlist, &trigdata);
/* Cleanup. */
list_free(runlist);
/*
* Make sure anything the event triggers did will be visible to the main
* command.
*/
CommandCounterIncrement();
}
/*
* Fire ddl_command_end triggers.
*/
void
EventTriggerDDLCommandEnd(Node *parsetree)
{
List *runlist;
EventTriggerData trigdata;
#if !defined(__EMSCRIPTEN__) && !defined(__wasi__)
/*
* See EventTriggerDDLCommandStart for a discussion about why event
* triggers are disabled in single user mode or via GUC.
*/
if (!IsUnderPostmaster || !event_triggers)
return;
#else
if (!event_triggers)
return;
#endif
/*
* Also do nothing if our state isn't set up, which it won't be if there
* weren't any relevant event triggers at the start of the current DDL
* command. This test might therefore seem optional, but it's important
* because EventTriggerCommonSetup might find triggers that didn't exist
* at the time the command started. Although this function itself
* wouldn't crash, the event trigger functions would presumably call
* pg_event_trigger_ddl_commands which would fail. Better to do nothing
* until the next command.
*/
if (!currentEventTriggerState)
return;
runlist = EventTriggerCommonSetup(parsetree,
EVT_DDLCommandEnd, "ddl_command_end",
&trigdata, false);
if (runlist == NIL)
return;
/*
* Make sure anything the main command did will be visible to the event
* triggers.
*/
CommandCounterIncrement();
/* Run the triggers. */
EventTriggerInvoke(runlist, &trigdata);
/* Cleanup. */
list_free(runlist);
}
/*
* Fire sql_drop triggers.
*/
void
EventTriggerSQLDrop(Node *parsetree)
{
List *runlist;
EventTriggerData trigdata;
#if !defined(__EMSCRIPTEN__) && !defined(__wasi__)
/*
* See EventTriggerDDLCommandStart for a discussion about why event
* triggers are disabled in single user mode or via a GUC.
*/
if (!IsUnderPostmaster || !event_triggers)
return;
#else
if (!event_triggers)
return;
#endif
/*
* Use current state to determine whether this event fires at all. If
* there are no triggers for the sql_drop event, then we don't have
* anything to do here. Note that dropped object collection is disabled
* if this is the case, so even if we were to try to run, the list would
* be empty.
*/
if (!currentEventTriggerState ||
slist_is_empty(¤tEventTriggerState->SQLDropList))
return;
runlist = EventTriggerCommonSetup(parsetree,
EVT_SQLDrop, "sql_drop",
&trigdata, false);
/*
* Nothing to do if run list is empty. Note this typically can't happen,
* because if there are no sql_drop events, then objects-to-drop wouldn't
* have been collected in the first place and we would have quit above.
* But it could occur if event triggers were dropped partway through.
*/
if (runlist == NIL)
return;
/*
* Make sure anything the main command did will be visible to the event
* triggers.
*/
CommandCounterIncrement();
/*
* Make sure pg_event_trigger_dropped_objects only works when running
* these triggers. Use PG_TRY to ensure in_sql_drop is reset even when
* one trigger fails. (This is perhaps not necessary, as the currentState
* variable will be removed shortly by our caller, but it seems better to
* play safe.)
*/
currentEventTriggerState->in_sql_drop = true;
/* Run the triggers. */
PG_TRY();
{
EventTriggerInvoke(runlist, &trigdata);
}
PG_FINALLY();
{
currentEventTriggerState->in_sql_drop = false;
}
PG_END_TRY();
/* Cleanup. */
list_free(runlist);
}
/*
* Fire login event triggers if any are present. The dathasloginevt
* pg_database flag is left unchanged when an event trigger is dropped to avoid
* complicating the codepath in the case of multiple event triggers. This
* function will instead unset the flag if no trigger is defined.
*/
void
EventTriggerOnLogin(void)
{
List *runlist;
EventTriggerData trigdata;
#if !defined(__EMSCRIPTEN__) && !defined(__wasi__)
/*
* See EventTriggerDDLCommandStart for a discussion about why event
* triggers are disabled in single user mode or via a GUC. We also need a
* database connection (some background workers don't have it).
*/
if (!IsUnderPostmaster || !event_triggers ||
!OidIsValid(MyDatabaseId) || !MyDatabaseHasLoginEventTriggers)
return;
#else
if (!event_triggers || !OidIsValid(MyDatabaseId) || !MyDatabaseHasLoginEventTriggers)
return;
#endif
StartTransactionCommand();
runlist = EventTriggerCommonSetup(NULL,
EVT_Login, "login",
&trigdata, false);
if (runlist != NIL)
{
/*
* Event trigger execution may require an active snapshot.
*/
PushActiveSnapshot(GetTransactionSnapshot());
/* Run the triggers. */
EventTriggerInvoke(runlist, &trigdata);
/* Cleanup. */
list_free(runlist);
PopActiveSnapshot();
}
/*
* There is no active login event trigger, but our
* pg_database.dathasloginevt is set. Try to unset this flag. We use the
* lock to prevent concurrent SetDatabaseHasLoginEventTriggers(), but we
* don't want to hang the connection waiting on the lock. Thus, we are
* just trying to acquire the lock conditionally.
*/
else if (ConditionalLockSharedObject(DatabaseRelationId, MyDatabaseId,
0, AccessExclusiveLock))
{
/*
* The lock is held. Now we need to recheck that login event triggers
* list is still empty. Once the list is empty, we know that even if
* there is a backend which concurrently inserts/enables a login event
* trigger, it will update pg_database.dathasloginevt *afterwards*.
*/
runlist = EventTriggerCommonSetup(NULL,
EVT_Login, "login",
&trigdata, true);
if (runlist == NIL)
{
Relation pg_db = table_open(DatabaseRelationId, RowExclusiveLock);
HeapTuple tuple;
void *state;
Form_pg_database db;
ScanKeyData key[1];
/* Fetch a copy of the tuple to scribble on */
ScanKeyInit(&key[0],
Anum_pg_database_oid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(MyDatabaseId));
systable_inplace_update_begin(pg_db, DatabaseOidIndexId, true,
NULL, 1, key, &tuple, &state);
if (!HeapTupleIsValid(tuple))
elog(ERROR, "could not find tuple for database %u", MyDatabaseId);
db = (Form_pg_database) GETSTRUCT(tuple);
if (db->dathasloginevt)
{
db->dathasloginevt = false;
/*
* Do an "in place" update of the pg_database tuple. Doing
* this instead of regular updates serves two purposes. First,
* that avoids possible waiting on the row-level lock. Second,
* that avoids dealing with TOAST.
*
* Changes made by inplace update may be lost due to
* concurrent normal updates; see inplace-inval.spec. However,
* we are OK with that. The subsequent connections will still
* have a chance to set "dathasloginevt" to false.
*/
systable_inplace_update_finish(state, tuple);
}
else