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Commit9dfdbef

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Adjust libpq to avoid deadlock when both client and server want to send
data, and both have filled the transmission buffers. One scenario wherethis can happen was illustrated here:http://archives.postgresql.org/pgsql-hackers/2003-04/msg00979.php
1 parentd5353ac commit9dfdbef

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2 files changed

+31
-3
lines changed

2 files changed

+31
-3
lines changed

‎src/interfaces/libpq/fe-exec.c

Lines changed: 12 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.151 2003/10/04 21:05:21 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.152 2003/10/19 21:36:41 tgl Exp $
1212
*
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*-------------------------------------------------------------------------
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*/
@@ -1336,6 +1336,17 @@ PQputCopyData(PGconn *conn, const char *buffer, int nbytes)
13361336
libpq_gettext("no COPY in progress\n"));
13371337
return-1;
13381338
}
1339+
1340+
/*
1341+
* Check for NOTICE messages coming back from the server. Since the
1342+
* server might generate multiple notices during the COPY, we have to
1343+
* consume those in a reasonably prompt fashion to prevent the comm
1344+
* buffers from filling up and possibly blocking the server.
1345+
*/
1346+
if (!PQconsumeInput(conn))
1347+
return-1;/* I/O failure */
1348+
parseInput(conn);
1349+
13391350
if (nbytes>0)
13401351
{
13411352
/*

‎src/interfaces/libpq/fe-misc.c

Lines changed: 19 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,7 @@
2323
* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
26-
* $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-misc.c,v 1.102 2003/08/08 21:42:55 momjian Exp $
26+
* $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-misc.c,v 1.103 2003/10/19 21:36:41 tgl Exp $
2727
*
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*-------------------------------------------------------------------------
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*/
@@ -828,7 +828,24 @@ pqSendSome(PGconn *conn, int len)
828828
break;
829829
}
830830

831-
if (pqWait(FALSE, TRUE,conn))
831+
/*
832+
* There are scenarios in which we can't send data because the
833+
* communications channel is full, but we cannot expect the server
834+
* to clear the channel eventually because it's blocked trying to
835+
* send data to us. (This can happen when we are sending a large
836+
* amount of COPY data, and the server has generated lots of
837+
* NOTICE responses.) To avoid a deadlock situation, we must be
838+
* prepared to accept and buffer incoming data before we try
839+
* again. Furthermore, it is possible that such incoming data
840+
* might not arrive until after we've gone to sleep. Therefore,
841+
* we wait for either read ready or write ready.
842+
*/
843+
if (pqReadData(conn)<0)
844+
{
845+
result=-1;/* error message already set up */
846+
break;
847+
}
848+
if (pqWait(TRUE, TRUE,conn))
832849
{
833850
result=-1;
834851
break;

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