From c6dbf1fe79287291bc260cbc06b0de419d2a198c Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 6 Jun 2016 14:52:58 -0400
Subject: [PATCH] Stop the executor if no more tuples can be sent from worker
to leader.
If a Gather node has read as many tuples as it needs (for example, due
to Limit) it may detach the queue connecting it to the worker before
reading all of the worker's tuples. Rather than let the worker
continue to generate and send all of the results, have it stop after
sending the next tuple.
More could be done here to stop the worker even quicker, but this is
about as well as we can hope to do for 9.6.
This is in response to a problem report from Andreas Seltenreich.
Commit 44339b892a04e94bbb472235882dc6f7023bdc65 should be actually be
sufficient to fix that example even without this change, but it seems
better to do this, too, since we might otherwise waste quite a large
amount of effort in one or more workers.
Discussion: CAA4eK1KOKGqmz9bGu+Z42qhRwMbm4R5rfnqsLCNqFs9j14jzEA@mail.gmail.com
Amit Kapila
---
src/backend/access/common/printtup.c | 22 +++++++++++++++-------
src/backend/commands/copy.c | 4 +++-
src/backend/commands/createas.c | 6 ++++--
src/backend/commands/matview.c | 6 ++++--
src/backend/executor/execMain.c | 10 +++++++++-
src/backend/executor/execTuples.c | 2 +-
src/backend/executor/functions.c | 6 ++++--
src/backend/executor/spi.c | 4 +++-
src/backend/executor/tqueue.c | 14 ++++++++++++--
src/backend/executor/tstoreReceiver.c | 12 ++++++++----
src/backend/tcop/dest.c | 3 ++-
src/backend/tcop/pquery.c | 8 +++++++-
src/include/access/printtup.h | 4 ++--
src/include/tcop/dest.h | 6 ++++--
14 files changed, 78 insertions(+), 29 deletions(-)
diff --git a/src/backend/access/common/printtup.c b/src/backend/access/common/printtup.c
index 1939ff5155b..d9664aa6c6b 100644
--- a/src/backend/access/common/printtup.c
+++ b/src/backend/access/common/printtup.c
@@ -26,9 +26,9 @@
static void printtup_startup(DestReceiver *self, int operation,
TupleDesc typeinfo);
-static void printtup(TupleTableSlot *slot, DestReceiver *self);
-static void printtup_20(TupleTableSlot *slot, DestReceiver *self);
-static void printtup_internal_20(TupleTableSlot *slot, DestReceiver *self);
+static bool printtup(TupleTableSlot *slot, DestReceiver *self);
+static bool printtup_20(TupleTableSlot *slot, DestReceiver *self);
+static bool printtup_internal_20(TupleTableSlot *slot, DestReceiver *self);
static void printtup_shutdown(DestReceiver *self);
static void printtup_destroy(DestReceiver *self);
@@ -299,7 +299,7 @@ printtup_prepare_info(DR_printtup *myState, TupleDesc typeinfo, int numAttrs)
* printtup --- print a tuple in protocol 3.0
* ----------------
*/
-static void
+static bool
printtup(TupleTableSlot *slot, DestReceiver *self)
{
TupleDesc typeinfo = slot->tts_tupleDescriptor;
@@ -376,13 +376,15 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
/* Return to caller's context, and flush row's temporary memory */
MemoryContextSwitchTo(oldcontext);
MemoryContextReset(myState->tmpcontext);
+
+ return true;
}
/* ----------------
* printtup_20 --- print a tuple in protocol 2.0
* ----------------
*/
-static void
+static bool
printtup_20(TupleTableSlot *slot, DestReceiver *self)
{
TupleDesc typeinfo = slot->tts_tupleDescriptor;
@@ -452,6 +454,8 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
/* Return to caller's context, and flush row's temporary memory */
MemoryContextSwitchTo(oldcontext);
MemoryContextReset(myState->tmpcontext);
+
+ return true;
}
/* ----------------
@@ -528,7 +532,7 @@ debugStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
* debugtup - print one tuple for an interactive backend
* ----------------
*/
-void
+bool
debugtup(TupleTableSlot *slot, DestReceiver *self)
{
TupleDesc typeinfo = slot->tts_tupleDescriptor;
@@ -553,6 +557,8 @@ debugtup(TupleTableSlot *slot, DestReceiver *self)
printatt((unsigned) i + 1, typeinfo->attrs[i], value);
}
printf("\t----\n");
+
+ return true;
}
/* ----------------
@@ -564,7 +570,7 @@ debugtup(TupleTableSlot *slot, DestReceiver *self)
* This is largely same as printtup_20, except we use binary formatting.
* ----------------
*/
-static void
+static bool
printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
{
TupleDesc typeinfo = slot->tts_tupleDescriptor;
@@ -636,4 +642,6 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
/* Return to caller's context, and flush row's temporary memory */
MemoryContextSwitchTo(oldcontext);
MemoryContextReset(myState->tmpcontext);
+
+ return true;
}
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 3201476c9e8..28dcd340017 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -4454,7 +4454,7 @@ copy_dest_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
/*
* copy_dest_receive --- receive one tuple
*/
-static void
+static bool
copy_dest_receive(TupleTableSlot *slot, DestReceiver *self)
{
DR_copy *myState = (DR_copy *) self;
@@ -4466,6 +4466,8 @@ copy_dest_receive(TupleTableSlot *slot, DestReceiver *self)
/* And send the data */
CopyOneRowTo(cstate, InvalidOid, slot->tts_values, slot->tts_isnull);
myState->processed++;
+
+ return true;
}
/*
diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index cb7a145ee5d..5a853c48a8b 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -62,7 +62,7 @@ typedef struct
static ObjectAddress CreateAsReladdr = {InvalidOid, InvalidOid, 0};
static void intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
-static void intorel_receive(TupleTableSlot *slot, DestReceiver *self);
+static bool intorel_receive(TupleTableSlot *slot, DestReceiver *self);
static void intorel_shutdown(DestReceiver *self);
static void intorel_destroy(DestReceiver *self);
@@ -482,7 +482,7 @@ intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
/*
* intorel_receive --- receive one tuple
*/
-static void
+static bool
intorel_receive(TupleTableSlot *slot, DestReceiver *self)
{
DR_intorel *myState = (DR_intorel *) self;
@@ -507,6 +507,8 @@ intorel_receive(TupleTableSlot *slot, DestReceiver *self)
myState->bistate);
/* We know this is a newly created relation, so there are no indexes */
+
+ return true;
}
/*
diff --git a/src/backend/commands/matview.c b/src/backend/commands/matview.c
index f00aab39e7b..62e61a26749 100644
--- a/src/backend/commands/matview.c
+++ b/src/backend/commands/matview.c
@@ -56,7 +56,7 @@ typedef struct
static int matview_maintenance_depth = 0;
static void transientrel_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
-static void transientrel_receive(TupleTableSlot *slot, DestReceiver *self);
+static bool transientrel_receive(TupleTableSlot *slot, DestReceiver *self);
static void transientrel_shutdown(DestReceiver *self);
static void transientrel_destroy(DestReceiver *self);
static void refresh_matview_datafill(DestReceiver *dest, Query *query,
@@ -467,7 +467,7 @@ transientrel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
/*
* transientrel_receive --- receive one tuple
*/
-static void
+static bool
transientrel_receive(TupleTableSlot *slot, DestReceiver *self)
{
DR_transientrel *myState = (DR_transientrel *) self;
@@ -486,6 +486,8 @@ transientrel_receive(TupleTableSlot *slot, DestReceiver *self)
myState->bistate);
/* We know this is a newly created relation, so there are no indexes */
+
+ return true;
}
/*
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index ac0230411c3..b5ced388d20 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -1593,7 +1593,15 @@ ExecutePlan(EState *estate,
* practice, this is probably always the case at this point.)
*/
if (sendTuples)
- (*dest->receiveSlot) (slot, dest);
+ {
+ /*
+ * If we are not able to send the tuple, we assume the destination
+ * has closed and no more tuples can be sent. If that's the case,
+ * end the loop.
+ */
+ if (!((*dest->receiveSlot) (slot, dest)))
+ break;
+ }
/*
* Count tuples processed, if this is a SELECT. (For other operation
diff --git a/src/backend/executor/execTuples.c b/src/backend/executor/execTuples.c
index 2b81f60a519..533050dc859 100644
--- a/src/backend/executor/execTuples.c
+++ b/src/backend/executor/execTuples.c
@@ -1266,7 +1266,7 @@ do_tup_output(TupOutputState *tstate, Datum *values, bool *isnull)
ExecStoreVirtualTuple(slot);
/* send the tuple to the receiver */
- (*tstate->dest->receiveSlot) (slot, tstate->dest);
+ (void) (*tstate->dest->receiveSlot) (slot, tstate->dest);
/* clean up */
ExecClearTuple(slot);
diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index 6e14c9d2967..cd93c045dcb 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -167,7 +167,7 @@ static Datum postquel_get_single_result(TupleTableSlot *slot,
static void sql_exec_error_callback(void *arg);
static void ShutdownSQLFunction(Datum arg);
static void sqlfunction_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
-static void sqlfunction_receive(TupleTableSlot *slot, DestReceiver *self);
+static bool sqlfunction_receive(TupleTableSlot *slot, DestReceiver *self);
static void sqlfunction_shutdown(DestReceiver *self);
static void sqlfunction_destroy(DestReceiver *self);
@@ -1904,7 +1904,7 @@ sqlfunction_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
/*
* sqlfunction_receive --- receive one tuple
*/
-static void
+static bool
sqlfunction_receive(TupleTableSlot *slot, DestReceiver *self)
{
DR_sqlfunction *myState = (DR_sqlfunction *) self;
@@ -1914,6 +1914,8 @@ sqlfunction_receive(TupleTableSlot *slot, DestReceiver *self)
/* Store the filtered tuple into the tuplestore */
tuplestore_puttupleslot(myState->tstore, slot);
+
+ return true;
}
/*
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 23cb6f407dd..7ccabdb44b2 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -1774,7 +1774,7 @@ spi_dest_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
* store tuple retrieved by Executor into SPITupleTable
* of current SPI procedure
*/
-void
+bool
spi_printtup(TupleTableSlot *slot, DestReceiver *self)
{
SPITupleTable *tuptable;
@@ -1809,6 +1809,8 @@ spi_printtup(TupleTableSlot *slot, DestReceiver *self)
(tuptable->free)--;
MemoryContextSwitchTo(oldcxt);
+
+ return true;
}
/*
diff --git a/src/backend/executor/tqueue.c b/src/backend/executor/tqueue.c
index 383b5352cba..8abb1f16e45 100644
--- a/src/backend/executor/tqueue.c
+++ b/src/backend/executor/tqueue.c
@@ -115,12 +115,13 @@ static RemapInfo *BuildRemapInfo(TupleDesc tupledesc);
* type over a range type over a range type over an array type over a record,
* or something like that.
*/
-static void
+static bool
tqueueReceiveSlot(TupleTableSlot *slot, DestReceiver *self)
{
TQueueDestReceiver *tqueue = (TQueueDestReceiver *) self;
TupleDesc tupledesc = slot->tts_tupleDescriptor;
HeapTuple tuple;
+ shm_mq_result result;
/*
* Test to see whether the tupledesc has changed; if so, set up for the
@@ -195,7 +196,16 @@ tqueueReceiveSlot(TupleTableSlot *slot, DestReceiver *self)
}
/* Send the tuple itself. */
- shm_mq_send(tqueue->handle, tuple->t_len, tuple->t_data, false);
+ result = shm_mq_send(tqueue->handle, tuple->t_len, tuple->t_data, false);
+
+ if (result == SHM_MQ_DETACHED)
+ return false;
+ else if (result != SHM_MQ_SUCCESS)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("unable to send tuples")));
+
+ return true;
}
/*
diff --git a/src/backend/executor/tstoreReceiver.c b/src/backend/executor/tstoreReceiver.c
index 516440ad32e..8f1e1b3f50c 100644
--- a/src/backend/executor/tstoreReceiver.c
+++ b/src/backend/executor/tstoreReceiver.c
@@ -37,8 +37,8 @@ typedef struct
} TStoreState;
-static void tstoreReceiveSlot_notoast(TupleTableSlot *slot, DestReceiver *self);
-static void tstoreReceiveSlot_detoast(TupleTableSlot *slot, DestReceiver *self);
+static bool tstoreReceiveSlot_notoast(TupleTableSlot *slot, DestReceiver *self);
+static bool tstoreReceiveSlot_detoast(TupleTableSlot *slot, DestReceiver *self);
/*
@@ -90,19 +90,21 @@ tstoreStartupReceiver(DestReceiver *self, int operation, TupleDesc typeinfo)
* Receive a tuple from the executor and store it in the tuplestore.
* This is for the easy case where we don't have to detoast.
*/
-static void
+static bool
tstoreReceiveSlot_notoast(TupleTableSlot *slot, DestReceiver *self)
{
TStoreState *myState = (TStoreState *) self;
tuplestore_puttupleslot(myState->tstore, slot);
+
+ return true;
}
/*
* Receive a tuple from the executor and store it in the tuplestore.
* This is for the case where we have to detoast any toasted values.
*/
-static void
+static bool
tstoreReceiveSlot_detoast(TupleTableSlot *slot, DestReceiver *self)
{
TStoreState *myState = (TStoreState *) self;
@@ -152,6 +154,8 @@ tstoreReceiveSlot_detoast(TupleTableSlot *slot, DestReceiver *self)
/* And release any temporary detoasted values */
for (i = 0; i < nfree; i++)
pfree(DatumGetPointer(myState->tofree[i]));
+
+ return true;
}
/*
diff --git a/src/backend/tcop/dest.c b/src/backend/tcop/dest.c
index 2c7dc6e5267..de45cbc4fb8 100644
--- a/src/backend/tcop/dest.c
+++ b/src/backend/tcop/dest.c
@@ -45,9 +45,10 @@
* dummy DestReceiver functions
* ----------------
*/
-static void
+static bool
donothingReceive(TupleTableSlot *slot, DestReceiver *self)
{
+ return true;
}
static void
diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index fcdc4c347c7..3f6cb12b4e5 100644
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -1109,7 +1109,13 @@ RunFromStore(Portal portal, ScanDirection direction, uint64 count,
if (!ok)
break;
- (*dest->receiveSlot) (slot, dest);
+ /*
+ * If we are not able to send the tuple, we assume the destination
+ * has closed and no more tuples can be sent. If that's the case,
+ * end the loop.
+ */
+ if (!((*dest->receiveSlot) (slot, dest)))
+ break;
ExecClearTuple(slot);
diff --git a/src/include/access/printtup.h b/src/include/access/printtup.h
index 64dde01cd14..608c5642872 100644
--- a/src/include/access/printtup.h
+++ b/src/include/access/printtup.h
@@ -25,11 +25,11 @@ extern void SendRowDescriptionMessage(TupleDesc typeinfo, List *targetlist,
extern void debugStartup(DestReceiver *self, int operation,
TupleDesc typeinfo);
-extern void debugtup(TupleTableSlot *slot, DestReceiver *self);
+extern bool debugtup(TupleTableSlot *slot, DestReceiver *self);
/* XXX these are really in executor/spi.c */
extern void spi_dest_startup(DestReceiver *self, int operation,
TupleDesc typeinfo);
-extern void spi_printtup(TupleTableSlot *slot, DestReceiver *self);
+extern bool spi_printtup(TupleTableSlot *slot, DestReceiver *self);
#endif /* PRINTTUP_H */
diff --git a/src/include/tcop/dest.h b/src/include/tcop/dest.h
index 4e42d61c37a..dd80433f74f 100644
--- a/src/include/tcop/dest.h
+++ b/src/include/tcop/dest.h
@@ -104,7 +104,9 @@ typedef enum
* pointers that the executor must call.
*
* Note: the receiveSlot routine must be passed a slot containing a TupleDesc
- * identical to the one given to the rStartup routine.
+ * identical to the one given to the rStartup routine. It returns bool where
+ * a "true" value means "continue processing" and a "false" value means
+ * "stop early, just as if we'd reached the end of the scan".
* ----------------
*/
typedef struct _DestReceiver DestReceiver;
@@ -112,7 +114,7 @@ typedef struct _DestReceiver DestReceiver;
struct _DestReceiver
{
/* Called for each tuple to be output: */
- void (*receiveSlot) (TupleTableSlot *slot,
+ bool (*receiveSlot) (TupleTableSlot *slot,
DestReceiver *self);
/* Per-executor-run initialization and shutdown: */
void (*rStartup) (DestReceiver *self,
--
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