Re: PostgreSQL vs MySQL : strange results on insertion - Mailing list pgsql-general

fpaul@netcourrier.com a écrit:
> Hello,
>
> I'm making some tests to migrate a MySQL DB to PostgreSQL DB. I realized a small program in C which does the same
thingfor MySQL (C API) and PostgreSQL (libpq) : 10000 insertion in a quite simple base. 
> My DB :
> |-----------------|----------------------------------------------|
> |                                test                           |
> | id              |  auto_increment (or serial for postgreSQL)  |
> | type_int        |  INT (or integer)                            |
> | type_varchar    |  varchar(255)                                |
> | type_int2    |  INT (or integer)                               |
> | type_text       |  text                                        |
> |-----------------|----------------------------------------------|
>
> /* -------------------- MySQL code : -------------------- */
> #define INSERTION "INSERT INTO test (type_int, type_varchar,type_tinyint,type_text) VALUES (%d,\'essai de chaine de
caractère\',100,\'MAJUSCULESet minuscules\'" 
>
> int main(int argc, char **argv) {
>     MYSQL mysql;
>     unsigned int i;
>     char mquery(1000);
>     MYSQL_RES *mysql_row;
>
>     mysql_init(&mysql);
>     if (mysql_real_connect(&mysql, NULL, "user", NULL, "bd", 0, NULL, 0)) {
>         for (i=0;i<=10000;i++) {
>             sprintf(mquery,INSERTION,i);
>             if ((mysql_query(&mysql,mquery)!=0) {
>                 printf("sql query error (%s) : %s\n",mquery,mysql_error(&mysql));
>                 mysql_close(&mysql);
>                 return 0;
>             }
>         }
>         mysql_close(&mysql);
>     }
>     else {
>         printf("sql connection error : %s\n",mysql_error(&mysql));
>         return 0;
>     }
>     return 0;
> }
>
> /* -------------------- PostgreSQL code : -------------------- */
> #define INSERTION "INSERT INTO test (type_int, type_varchar,type_tinyint,type_text) VALUES (%d,\'essai de chaine de
caractère\',100,\'MAJUSCULESet minuscules\'" 
>
> int main(int argc, char **argv) {
>     PGconn *conn;
>     unsigned int i;
>     char mquery(1000);
>     PGresult *res;
>
>     conn=PQconnectdb("dbname=db user=user");
>     if (PQstatus(conn) == CONNECTION_OK) {
>         for (i=0;i<=10000;i++) {
>             sprintf(mquery,INSERTION,i);
>             res=PQexec(conn,mquery);
>             if (PQresultstatus(res)!= PGRES_COMMAND_OK) {
>                 printf("sql query error (%s) : %s\n",mquery,PQresultErrorMessage(res));
>                 PQclear(res);
>                 PQfinish(conn);
>                 return 0;
>             }
>         }
>         PQclear(res);
>         PQfinish(conn);
>     }
>     else {
>         printf("sql connection error : %s\n",PQerrorMessage(conn));
>         return 0;
>     }
>     return 0;
> }
>
> I launch these programs on my computer : Linux Debian with MySQL 3.23.51 and PostgreSQL 7.2.1 (installation by
defaultwith 'apt-get install'). 
> Time to realize 10000 insertions with MySQL:
>     $ time ./test__mysql
>
>     real  0m1.500s
>     user 0m0.150s
>     sys   0m0.090s
> (between 1 and 2 seconds)
>
> Time to realize 10000 insertions with PostgreSQL:
>     $time ./test_postgresql
>
>     real  0m28.568s
>     user 0m0.390s
>     sys   0m0.270s
> (between 28 and 30 seconds !!!.... )
>
> Very strange, isn't it ? Is there something in PostgreSQL's C API that I didn't understand ? Subtleties during the
configuration? I do not want to believe that PostgreSQL is 15 times slower than MySQL ! 
> Thank you for any comment, remark and correction!
>
> Florent Paul

pgsql launches 10000 transactions (I don't know if mysql does this)
You should launch a "BEGIN;" before your 10000 insert and an "END;" after.
or better: test your server and discover the proper number of insert
to be done in one transaction to have the max speed.
For mine, 3000 insert for each transaction is good.