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Fix memory leak in printtup.c.

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Commit f2dec34e1 changed things so that printtup's output stringinfo
buffer was allocated outside the per-row temporary context, not inside
it.  This creates a need to free that buffer explicitly when the temp
context is freed, but that was overlooked.  In most cases, this is all
happening inside a portal or executor context that will go away shortly
anyhow, but that's not always true.  Notably, the stringinfo ends up
getting leaked when JDBC uses row-at-a-time fetches.  For a query
that returns wide rows, that adds up after awhile.

Per bug #15700 from Matthias Otterbach.  Back-patch to v11 where the
faulty code was added.

Discussion: https://postgr.es/m/15700-8c408321a87d56bb@postgresql.org
This commit is contained in:
Tom Lane 2019-03-18 17:54:24 -04:00
parent fc8b39a46e
commit adf27de8ea
1 changed files with 10 additions and 2 deletions
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12
src/backend/access/common/printtup.c
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@ -61,12 +61,12 @@ typedef struct
typedef struct
{
DestReceiver pub; /* publicly-known function pointers */
StringInfoData buf; /* output buffer */
Portal portal; /* the Portal we are printing from */
bool sendDescrip; /* send RowDescription at startup? */
TupleDesc attrinfo; /* The attr info we are set up for */
int nattrs;
PrinttupAttrInfo *myinfo; /* Cached info about each attr */
StringInfoData buf; /* output buffer (*not* in tmpcontext) */
MemoryContext tmpcontext; /* Memory context for per-row workspace */
} DR_printtup;
@ -94,6 +94,7 @@ printtup_create_DR(CommandDest dest)
self->attrinfo = NULL;
self->nattrs = 0;
self->myinfo = NULL;
self->buf.data = NULL;
self->tmpcontext = NULL;
return (DestReceiver *) self;
@ -132,7 +133,10 @@ printtup_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
DR_printtup *myState = (DR_printtup *) self;
Portal portal = myState->portal;
/* create buffer to be used for all messages */
/*
* Create I/O buffer to be used for all messages. This cannot be inside
* tmpcontext, since we want to re-use it across rows.
*/
initStringInfo(&myState->buf);
/*
@ -544,6 +548,10 @@ printtup_shutdown(DestReceiver *self)
myState->attrinfo = NULL;
if (myState->buf.data)
pfree(myState->buf.data);
myState->buf.data = NULL;
if (myState->tmpcontext)
MemoryContextDelete(myState->tmpcontext);
myState->tmpcontext = NULL;