Hi fellow hackers,
Please find attached to this email a patch to implement a new Event
Trigger, fired on the the "table_rewrite" event. As attached, it's meant
as a discussion enabler and only supports ALTER TABLE (and maybe not in
all forms of it). It will need to grow support for VACUUM FULL and
CLUSTER and more before getting commited.
Also, I'd like to work on the AccessExclusiveLock Event Trigger next,
but wanted this one, more simple, to get acceptance as the way to
approach adding events that are not DDL centric.
This time it's not about which command is running, it's about what the
command is doing.
src/backend/commands/event_trigger.c | 92 ++++++++++++++++++++-
src/backend/commands/tablecmds.c | 35 +++++++-
src/backend/utils/cache/evtcache.c | 2 +
src/include/commands/event_trigger.h | 1 +
src/include/utils/evtcache.h | 3 +-
src/test/regress/expected/event_trigger.out | 18 ++++
src/test/regress/sql/event_trigger.sql | 21 +++++
7 files changed, 166 insertions(+), 6 deletions(-)
Regards,
--
Dimitri Fontaine 06 63 07 10 78
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 1b8c94b..9314da9 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -119,11 +119,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
HeapTuple tup,
Oid newOwnerId);
static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+ const char *tag);
static void error_duplicate_filter_variable(const char *defname);
static Datum filter_list_to_array(List *filterlist);
static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
Oid evtOwner, Oid funcoid, List *tags);
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);
/*
@@ -154,7 +157,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
/* 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, "sql_drop") != 0 &&
+ strcmp(stmt->eventname, "table_rewrite") != 0)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("unrecognized event name \"%s\"",
@@ -183,6 +187,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
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);
/*
* Give user a nice error message if an event trigger of the same name
@@ -281,6 +288,40 @@ check_ddl_tag(const char *tag)
}
/*
+ * Validate DDL command tags.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+ ListCell *lc;
+
+ foreach(lc, taglist)
+ {
+ const char *tag = strVal(lfirst(lc));
+ event_trigger_command_tag_check_result result;
+
+ result = check_table_rewrite_ddl_tag(tag);
+ if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ /* translator: %s represents an SQL statement name */
+ errmsg("event triggers are not supported for %s",
+ tag)));
+ }
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+ if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+ pg_strcasecmp(tag, "CLUSTER") == 0 ||
+ pg_strcasecmp(tag, "VACUUM") == 0)
+ return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+ return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
* Complain about a duplicate filter variable.
*/
static void
@@ -838,6 +879,55 @@ EventTriggerSQLDrop(Node *parsetree)
list_free(runlist);
}
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree)
+{
+ List *runlist;
+ EventTriggerData trigdata;
+
+ /*
+ * 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.)
+ */
+ if (!IsUnderPostmaster)
+ return;
+
+ runlist = EventTriggerCommonSetup(parsetree,
+ EVT_TableRewrite,
+ "table_rewrite",
+ &trigdata);
+ 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();
+}
+
/*
* Invoke each event trigger in a list of event triggers.
*/
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ecdff1e..a381c33 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
#include "commands/cluster.h"
#include "commands/comment.h"
#include "commands/defrem.h"
+#include "commands/event_trigger.h"
#include "commands/policy.h"
#include "commands/sequence.h"
#include "commands/tablecmds.h"
@@ -303,7 +304,8 @@ static void validateForeignKeyConstraint(char *conname,
static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
Constraint *fkconstraint,
Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+ Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
bool recurse, bool recursing, LOCKMODE lockmode);
static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
@@ -2723,7 +2725,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
CheckTableNotInUse(rel, "ALTER TABLE");
- ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+ ATController(stmt,
+ rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
lockmode);
}
@@ -2746,7 +2749,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
rel = relation_open(relid, lockmode);
- ATController(rel, cmds, recurse, lockmode);
+ ATController(NULL, rel, cmds, recurse, lockmode);
}
/*
@@ -3015,10 +3018,12 @@ AlterTableGetLockLevel(List *cmds)
}
static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+ Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
{
List *wqueue = NIL;
ListCell *lcmd;
+ ListCell *ltab;
/* Phase 1: preliminary examination of commands, create work queue */
foreach(lcmd, cmds)
@@ -3031,6 +3036,28 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
/* Close the relation, but keep lock until commit */
relation_close(rel, NoLock);
+ /*
+ * If a rewrite is needed, fire off an Event Trigger now.
+ *
+ * We don't support Event Trigger for nested commands anywhere, here
+ * included, and parstree is given NULL when comming from
+ * AlterTableInternal.
+ */
+ if (parsetree)
+ {
+ foreach(ltab, wqueue)
+ {
+ AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
+
+ if (tab->rewrite)
+ {
+ /* we don't have no parsetree to provide for here. */
+ EventTriggerTableRewrite(parsetree);
+ break;
+ }
+ }
+ }
+
/* Phase 2: update system catalogs */
ATRewriteCatalogs(&wqueue, lockmode);
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
event = EVT_DDLCommandEnd;
else if (strcmp(evtevent, "sql_drop") == 0)
event = EVT_SQLDrop;
+ else if (strcmp(evtevent, "table_rewrite") == 0)
+ event = EVT_TableRewrite;
else
continue;
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..d7e2958 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
extern void EventTriggerDDLCommandStart(Node *parsetree);
extern void EventTriggerDDLCommandEnd(Node *parsetree);
extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree);
extern bool EventTriggerBeginCompleteQuery(void);
extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
{
EVT_DDLCommandStart,
EVT_DDLCommandEnd,
- EVT_SQLDrop
+ EVT_SQLDrop,
+ EVT_TableRewrite
} EventTriggerEvent;
typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..ec80170 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,21 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
DROP ROLE regression_bob;
DROP EVENT TRIGGER regress_event_trigger_drop_objects;
DROP EVENT TRIGGER undroppable;
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+ RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+ execute procedure test_evtrig_no_rewrite();
+create table rewriteme (foo float);
+insert into rewriteme
+ select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR: I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..90b3d7e 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,24 @@ DROP ROLE regression_bob;
DROP EVENT TRIGGER regress_event_trigger_drop_objects;
DROP EVENT TRIGGER undroppable;
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+ RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+ execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (foo float);
+insert into rewriteme
+ select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
--
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