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Commiteb15f53

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committed
Improve libpq's error recovery for connection loss during COPY.
In pqSendSome, if the connection is already closed at entry, discard anyqueued output data before returning. There is no possibility of eversending the data, and anyway this corresponds to what we'd do if we'ddetected a hard error while trying to send(). This avoids possibleindefinite bloat of the output buffer if the application keeps tryingto send data (or even just keeps trying to do PQputCopyEnd, as psqlindeed will).Because PQputCopyEnd won't transition out of PGASYNC_COPY_IN stateuntil it's successfully queued the COPY END message, and pqPutMsgEnddoesn't distinguish a queuing failure from a pqSendSome failure,this omission allowed an infinite loop in psql if the connection closureoccurred when we had at least 8K queued to send. It might be worthrefactoring so that we can make that distinction, but for the momentthe other changes made here seem to offer adequate defenses.To guard against other variants of this scenario, do not allowPQgetResult to return a PGRES_COPY_XXX result if the connection isalready known dead. Make sure it returns PGRES_FATAL_ERROR instead.Per report from Stephen Frost. Back-patch to all active branches.
1 parenta69cc9b commiteb15f53

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2 files changed

+36
-12
lines changed

2 files changed

+36
-12
lines changed

‎src/interfaces/libpq/fe-exec.c

Lines changed: 34 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -61,6 +61,7 @@ static int PQsendQueryGuts(PGconn *conn,
6161
constint*paramFormats,
6262
intresultFormat);
6363
staticvoidparseInput(PGconn*conn);
64+
staticPGresult*getCopyResult(PGconn*conn,ExecStatusTypecopytype);
6465
staticboolPQexecStart(PGconn*conn);
6566
staticPGresult*PQexecFinish(PGconn*conn);
6667
staticintPQsendDescribe(PGconn*conn,chardesc_type,
@@ -1563,22 +1564,13 @@ PQgetResult(PGconn *conn)
15631564
conn->asyncStatus=PGASYNC_BUSY;
15641565
break;
15651566
casePGASYNC_COPY_IN:
1566-
if (conn->result&&conn->result->resultStatus==PGRES_COPY_IN)
1567-
res=pqPrepareAsyncResult(conn);
1568-
else
1569-
res=PQmakeEmptyPGresult(conn,PGRES_COPY_IN);
1567+
res=getCopyResult(conn,PGRES_COPY_IN);
15701568
break;
15711569
casePGASYNC_COPY_OUT:
1572-
if (conn->result&&conn->result->resultStatus==PGRES_COPY_OUT)
1573-
res=pqPrepareAsyncResult(conn);
1574-
else
1575-
res=PQmakeEmptyPGresult(conn,PGRES_COPY_OUT);
1570+
res=getCopyResult(conn,PGRES_COPY_OUT);
15761571
break;
15771572
casePGASYNC_COPY_BOTH:
1578-
if (conn->result&&conn->result->resultStatus==PGRES_COPY_BOTH)
1579-
res=pqPrepareAsyncResult(conn);
1580-
else
1581-
res=PQmakeEmptyPGresult(conn,PGRES_COPY_BOTH);
1573+
res=getCopyResult(conn,PGRES_COPY_BOTH);
15821574
break;
15831575
default:
15841576
printfPQExpBuffer(&conn->errorMessage,
@@ -1615,6 +1607,36 @@ PQgetResult(PGconn *conn)
16151607
returnres;
16161608
}
16171609

1610+
/*
1611+
* getCopyResult
1612+
* Helper for PQgetResult: generate result for COPY-in-progress cases
1613+
*/
1614+
staticPGresult*
1615+
getCopyResult(PGconn*conn,ExecStatusTypecopytype)
1616+
{
1617+
/*
1618+
* If the server connection has been lost, don't pretend everything is
1619+
* hunky-dory; instead return a PGRES_FATAL_ERROR result, and reset the
1620+
* asyncStatus to idle (corresponding to what we'd do if we'd detected I/O
1621+
* error in the earlier steps in PQgetResult).The text returned in the
1622+
* result is whatever is in conn->errorMessage; we hope that was filled
1623+
* with something relevant when the lost connection was detected.
1624+
*/
1625+
if (conn->status!=CONNECTION_OK)
1626+
{
1627+
pqSaveErrorResult(conn);
1628+
conn->asyncStatus=PGASYNC_IDLE;
1629+
returnpqPrepareAsyncResult(conn);
1630+
}
1631+
1632+
/* If we have an async result for the COPY, return that */
1633+
if (conn->result&&conn->result->resultStatus==copytype)
1634+
returnpqPrepareAsyncResult(conn);
1635+
1636+
/* Otherwise, invent a suitable PGresult */
1637+
returnPQmakeEmptyPGresult(conn,copytype);
1638+
}
1639+
16181640

16191641
/*
16201642
* PQexec

‎src/interfaces/libpq/fe-misc.c

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -782,6 +782,8 @@ pqSendSome(PGconn *conn, int len)
782782
{
783783
printfPQExpBuffer(&conn->errorMessage,
784784
libpq_gettext("connection not open\n"));
785+
/* Discard queued data; no chance it'll ever be sent */
786+
conn->outCount=0;
785787
return-1;
786788
}
787789

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