Re: sqlite3 dbd provider question

[Chris Darroch]

William A. Rowe, Jr. wrote:

 Are you referring to the Oracle dbd driver prepared-statement cache?

yes; my question is, even if we do construct a cache, is module lifetime
appropriate?  When accessed by several different consumers at once?  (e.g.
two libraries that rely on dbd, or several different httpd modules and
applications which consume dbd?).

  This cache code has always been disabled, IIRC.  The
#define GLOBAL_PREPARED_STATEMENTS is commented out, I believe, and
personally I've never tried un-commenting it.  I suspect that (as Nick
Kew's comments indicate) it's not ready for use.

  One option, therefore, would be remove it and all the related
code, specifically the notion of a cache of prepared statements
(which has problems in a multiple-provider context, as you've pointed out).

  In a related fix, at a minimum, all the apr_dbd_mutex_unlock() calls
should be wrapped in #ifdef GLOBAL_PREPARED_STATEMENTS macros
(as things stand now).  See the patch below for line locations.
Or, if GLOBAL_PREPARED_STATEMENTS is being cut out entirely, these
calls should also be removed; they're not correct on their own.

  I have a few patches like this in the queue, in particular, I worked
through the hoops necessary to get proper Oracle-style UTF-8 handling
for LOBs.  Unfortunately that was with an earlier version (circa 1.2)
and it will take me a while to port them to the 1.3/trunk version;
it's on the to-do list for the next month but I shouldn't make any
promises.  I'll see if I can speed this up, though.

Chris.

=========================
--- apr_dbd_oracle.c.orig       2008-05-19 16:08:36.000000000 -0700
+++ apr_dbd_oracle.c    2008-04-09 15:17:32.000000000 -0700
@@ -982,9 +982,7 @@
    sql->status = OCIHandleAlloc(dbd_oracle_env, (dvoid**) &stmt->stmt,
                                 OCI_HTYPE_STMT, 0, NULL);
    if (sql->status != OCI_SUCCESS) {
-#ifdef GLOBAL_PREPARED_STATEMENTS
        apr_dbd_mutex_unlock();
-#endif
        return 1;
    }

@@ -992,9 +990,7 @@
                                 strlen(query), OCI_NTV_SYNTAX, OCI_DEFAULT);
    if (sql->status != OCI_SUCCESS) {
        OCIHandleFree(stmt->stmt, OCI_HTYPE_STMT);
-#ifdef GLOBAL_PREPARED_STATEMENTS
        apr_dbd_mutex_unlock();
-#endif
        return 1;
    }

@@ -1005,9 +1001,7 @@
    sql->status = OCIAttrGet(stmt->stmt, OCI_HTYPE_STMT, &stmt->type, 0,
                             OCI_ATTR_STMT_TYPE, sql->err);
    if (sql->status != OCI_SUCCESS) {
-#ifdef GLOBAL_PREPARED_STATEMENTS
        apr_dbd_mutex_unlock();
-#endif
        return 1;
    }

@@ -1017,9 +1011,7 @@
                             sizeof(prefetch_size), OCI_ATTR_PREFETCH_MEMORY,
                             sql->err);
    if (sql->status != OCI_SUCCESS) {
-#ifdef GLOBAL_PREPARED_STATEMENTS
        apr_dbd_mutex_unlock();
-#endif
        return 1;
    }
#endif