From 3f064e505db2bf70e1045de243c8d36b3167a0ec Mon Sep 17 00:00:00 2001
From: Yugo Nagata <nagata@sraoss.co.jp>
Date: Fri, 20 Dec 2019 10:09:45 +0900
Subject: [PATCH v24 04/15] Allow to prolong life span of transition tables
 until transaction end

Originally, tuplestores of AFTER trigger's transition tables were
freed for each query depth. For our IVM implementation, we would like
to prolong life of the tuplestores because we have to preserve them
for a whole query assuming that some base tables might be changed
in some trigger functions.
---
 src/backend/commands/trigger.c | 80 +++++++++++++++++++++++++++++++++-
 src/include/commands/trigger.h |  2 +
 2 files changed, 80 insertions(+), 2 deletions(-)

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index d8890d2c74..c7a2bc3ed8 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -3570,6 +3570,10 @@ typedef struct AfterTriggerEventList
  * end of the list, so it is relatively easy to discard them.  The event
  * list chunks themselves are stored in event_cxt.
  *
+ * prolonged_tuplestored is a list of transition table tuplestores whose
+ * life are prolonged to the end of the outmost query instead of each nested
+ * query.
+ *
  * query_depth is the current depth of nested AfterTriggerBeginQuery calls
  * (-1 when the stack is empty).
  *
@@ -3635,6 +3639,7 @@ typedef struct AfterTriggersData
 	SetConstraintState state;	/* the active S C state */
 	AfterTriggerEventList events;	/* deferred-event list */
 	MemoryContext event_cxt;	/* memory context for events, if any */
+	List   *prolonged_tuplestores;	/* list of prolonged tuplestores */
 
 	/* per-query-level data: */
 	AfterTriggersQueryData *query_stack;	/* array of structs shown below */
@@ -3670,6 +3675,7 @@ struct AfterTriggersTableData
 	bool		closed;			/* true when no longer OK to add tuples */
 	bool		before_trig_done;	/* did we already queue BS triggers? */
 	bool		after_trig_done;	/* did we already queue AS triggers? */
+	bool		prolonged;			/* are transition tables prolonged? */
 	AfterTriggerEventList after_trig_events;	/* if so, saved list pointer */
 	Tuplestorestate *old_tuplestore;	/* "old" transition table, if any */
 	Tuplestorestate *new_tuplestore;	/* "new" transition table, if any */
@@ -4448,6 +4454,45 @@ afterTriggerInvokeEvents(AfterTriggerEventList *events,
 }
 
 
+/*
+ * SetTransitionTablePreserved
+ *
+ * Prolong lifespan of transition tables corresponding specified relid and
+ * command type to the end of the outmost query instead of each nested query.
+ * This enables to use nested AFTER trigger's transition tables from outer
+ * query's triggers.  Currently, only immediate incremental view maintenance
+ * uses this.
+ */
+void
+SetTransitionTablePreserved(Oid relid, CmdType cmdType)
+{
+	AfterTriggersTableData *table;
+	AfterTriggersQueryData *qs;
+	bool		found = false;
+	ListCell   *lc;
+
+	/* Check state, like AfterTriggerSaveEvent. */
+	if (afterTriggers.query_depth < 0)
+		elog(ERROR, "SetTransitionTablePreserved() called outside of query");
+
+	qs = &afterTriggers.query_stack[afterTriggers.query_depth];
+
+	foreach(lc, qs->tables)
+	{
+		table = (AfterTriggersTableData *) lfirst(lc);
+		if (table->relid == relid && table->cmdType == cmdType &&
+			table->closed)
+		{
+			table->prolonged = true;
+			found = true;
+		}
+	}
+
+	if (!found)
+		elog(ERROR,"could not find table with OID %d and command type %d", relid, cmdType);
+}
+
+
 /*
  * GetAfterTriggersTableData
  *
@@ -4642,6 +4687,7 @@ AfterTriggerBeginXact(void)
 	 */
 	afterTriggers.firing_counter = (CommandId) 1;	/* mustn't be 0 */
 	afterTriggers.query_depth = -1;
+	afterTriggers.prolonged_tuplestores = NIL;
 
 	/*
 	 * Verify that there is no leftover state remaining.  If these assertions
@@ -4802,11 +4848,29 @@ AfterTriggerFreeQuery(AfterTriggersQueryData *qs)
 		ts = table->old_tuplestore;
 		table->old_tuplestore = NULL;
 		if (ts)
-			tuplestore_end(ts);
+		{
+			if (table->prolonged && afterTriggers.query_depth > 0)
+			{
+				MemoryContext oldcxt = MemoryContextSwitchTo(CurTransactionContext);
+				afterTriggers.prolonged_tuplestores = lappend(afterTriggers.prolonged_tuplestores, ts);
+				MemoryContextSwitchTo(oldcxt);
+			}
+			else
+				tuplestore_end(ts);
+		}
 		ts = table->new_tuplestore;
 		table->new_tuplestore = NULL;
 		if (ts)
-			tuplestore_end(ts);
+		{
+			if (table->prolonged && afterTriggers.query_depth > 0)
+			{
+				MemoryContext oldcxt = MemoryContextSwitchTo(CurTransactionContext);
+				afterTriggers.prolonged_tuplestores = lappend(afterTriggers.prolonged_tuplestores, ts);
+				MemoryContextSwitchTo(oldcxt);
+			}
+			else
+				tuplestore_end(ts);
+		}
 		if (table->storeslot)
 			ExecDropSingleTupleTableSlot(table->storeslot);
 	}
@@ -4818,6 +4882,18 @@ AfterTriggerFreeQuery(AfterTriggersQueryData *qs)
 	 */
 	qs->tables = NIL;
 	list_free_deep(tables);
+
+	/* Release prolonged tuplestores at the end of the outmost query */
+	if (afterTriggers.query_depth == 0)
+	{
+		foreach(lc, afterTriggers.prolonged_tuplestores)
+		{
+			ts = (Tuplestorestate *) lfirst(lc);
+			if (ts)
+				tuplestore_end(ts);
+		}
+		afterTriggers.prolonged_tuplestores = NIL;
+	}
 }
 
 
diff --git a/src/include/commands/trigger.h b/src/include/commands/trigger.h
index 9ef7f6d768..0cfb0b3c5c 100644
--- a/src/include/commands/trigger.h
+++ b/src/include/commands/trigger.h
@@ -251,6 +251,8 @@ extern void AfterTriggerEndSubXact(bool isCommit);
 extern void AfterTriggerSetState(ConstraintsSetStmt *stmt);
 extern bool AfterTriggerPendingOnRel(Oid relid);
 
+extern void SetTransitionTablePreserved(Oid relid, CmdType cmdType);
+
 
 /*
  * in utils/adt/ri_triggers.c
-- 
2.17.1