Re: vacuumlo - use a cursor - Mailing list pgsql-hackers

Nobody seemed interested. But I do think it's a good idea still.

cheers

andrew



On 06/29/2013 11:23 AM, Bruce Momjian wrote:
> Is there a reason this patch was not applied?
>
> ---------------------------------------------------------------------------
>
> On Mon, Nov 12, 2012 at 05:14:57PM -0500, Andrew Dunstan wrote:
>> vacuumlo is rather simpleminded about dealing with the list of LOs
>> to be removed - it just fetches them as a straight resultset. For
>> one of my our this resulted in an out of memory condition. The
>> attached patch tries to remedy that by using a cursor instead. If
>> this is wanted I will add it to the next commitfest. The actualy
>> changes are very small - most of the patch is indentation changes
>> due to the introduction of an extra loop.
>>
>> cheers
>>
>> andrew
>> *** a/contrib/vacuumlo/vacuumlo.c
>> --- b/contrib/vacuumlo/vacuumlo.c
>> ***************
>> *** 290,362 **** vacuumlo(const char *database, const struct _param * param)
>>        PQclear(res);
>>    
>>        buf[0] = '\0';
>> !     strcat(buf, "SELECT lo FROM vacuum_l");
>> !     res = PQexec(conn, buf);
>> !     if (PQresultStatus(res) != PGRES_TUPLES_OK)
>> !     {
>> !         fprintf(stderr, "Failed to read temp table:\n");
>> !         fprintf(stderr, "%s", PQerrorMessage(conn));
>> !         PQclear(res);
>>            PQfinish(conn);
>>            return -1;
>> !     }
>>    
>> -     matched = PQntuples(res);
>>        deleted = 0;
>> !     for (i = 0; i < matched; i++)
>>        {
>> !         Oid            lo = atooid(PQgetvalue(res, i, 0));
>>    
>> !         if (param->verbose)
>>            {
>> !             fprintf(stdout, "\rRemoving lo %6u   ", lo);
>> !             fflush(stdout);
>>            }
>>    
>> !         if (param->dry_run == 0)
>>            {
>> !             if (lo_unlink(conn, lo) < 0)
>>                {
>> !                 fprintf(stderr, "\nFailed to remove lo %u: ", lo);
>> !                 fprintf(stderr, "%s", PQerrorMessage(conn));
>> !                 if (PQtransactionStatus(conn) == PQTRANS_INERROR)
>>                    {
>> !                     success = false;
>> !                     break;
>>                    }
>>                }
>>                else
>>                    deleted++;
>> !         }
>> !         else
>> !             deleted++;
>> !         if (param->transaction_limit > 0 &&
>> !             (deleted % param->transaction_limit) == 0)
>> !         {
>> !             res2 = PQexec(conn, "commit");
>> !             if (PQresultStatus(res2) != PGRES_COMMAND_OK)
>>                {
>> !                 fprintf(stderr, "Failed to commit transaction:\n");
>> !                 fprintf(stderr, "%s", PQerrorMessage(conn));
>>                    PQclear(res2);
>> !                 PQclear(res);
>> !                 PQfinish(conn);
>> !                 return -1;
>> !             }
>> !             PQclear(res2);
>> !             res2 = PQexec(conn, "begin");
>> !             if (PQresultStatus(res2) != PGRES_COMMAND_OK)
>> !             {
>> !                 fprintf(stderr, "Failed to start transaction:\n");
>> !                 fprintf(stderr, "%s", PQerrorMessage(conn));
>>                    PQclear(res2);
>> -                 PQclear(res);
>> -                 PQfinish(conn);
>> -                 return -1;
>>                }
>> -             PQclear(res2);
>>            }
>>        }
>>        PQclear(res);
>>    
>>        /*
>> --- 290,389 ----
>>        PQclear(res);
>>    
>>        buf[0] = '\0';
>> !     strcat(buf,
>> !            "DECLARE myportal CURSOR WITH HOLD FOR SELECT lo FROM vacuum_l");
>> !     res = PQexec(conn, buf);
>> !     if (PQresultStatus(res) != PGRES_COMMAND_OK)
>> !     {
>> !         fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));
>> !         PQclear(res);
>>            PQfinish(conn);
>>            return -1;
>> !     }
>> !     PQclear(res);
>> !
>> !     snprintf(buf, BUFSIZE, "FETCH FORWARD " INT64_FORMAT " IN myportal",
>> !              param->transaction_limit > 0 ? param->transaction_limit : 1000);
>>    
>>        deleted = 0;
>> !
>> !     while (1)
>>        {
>> !         res = PQexec(conn, buf);
>> !         if (PQresultStatus(res) != PGRES_TUPLES_OK)
>> !         {
>> !             fprintf(stderr, "Failed to read temp table:\n");
>> !             fprintf(stderr, "%s", PQerrorMessage(conn));
>> !             PQclear(res);
>> !             PQfinish(conn);
>> !             return -1;
>> !         }
>>    
>> !         matched = PQntuples(res);
>> !
>> !         if (matched <= 0)
>>            {
>> !             /* at end of resultset */
>> !             break;
>>            }
>>    
>> !         for (i = 0; i < matched; i++)
>>            {
>> !             Oid            lo = atooid(PQgetvalue(res, i, 0));
>> !             
>> !             if (param->verbose)
>> !             {
>> !                 fprintf(stdout, "\rRemoving lo %6u   ", lo);
>> !                 fflush(stdout);
>> !             }
>> !             
>> !             if (param->dry_run == 0)
>>                {
>> !                 if (lo_unlink(conn, lo) < 0)
>>                    {
>> !                     fprintf(stderr, "\nFailed to remove lo %u: ", lo);
>> !                     fprintf(stderr, "%s", PQerrorMessage(conn));
>> !                     if (PQtransactionStatus(conn) == PQTRANS_INERROR)
>> !                     {
>> !                         success = false;
>> !                         break;
>> !                     }
>>                    }
>> +                 else
>> +                     deleted++;
>>                }
>>                else
>>                    deleted++;
>> !
>> !             if (param->transaction_limit > 0 &&
>> !                 (deleted % param->transaction_limit) == 0)
>>                {
>> !                 res2 = PQexec(conn, "commit");
>> !                 if (PQresultStatus(res2) != PGRES_COMMAND_OK)
>> !                 {
>> !                     fprintf(stderr, "Failed to commit transaction:\n");
>> !                     fprintf(stderr, "%s", PQerrorMessage(conn));
>> !                     PQclear(res2);
>> !                     PQclear(res);
>> !                     PQfinish(conn);
>> !                     return -1;
>> !                 }
>>                    PQclear(res2);
>> !                 res2 = PQexec(conn, "begin");
>> !                 if (PQresultStatus(res2) != PGRES_COMMAND_OK)
>> !                 {
>> !                     fprintf(stderr, "Failed to start transaction:\n");
>> !                     fprintf(stderr, "%s", PQerrorMessage(conn));
>> !                     PQclear(res2);
>> !                     PQclear(res);
>> !                     PQfinish(conn);
>> !                     return -1;
>> !                 }
>>                    PQclear(res2);
>>                }
>>            }
>>        }
>> +
>>        PQclear(res);
>>    
>>        /*
>> -- 
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