Re: [HACKERS] Proposal: new large object API - Mailing list pgsql-patches

Here is the proposed patches. If there's no objection, I will
commit(or Shall I wait for next "commit festa"?).

Note that I decide to use lo_import_with_oid, but the signature is
changed(the second and the third arguments are swapped because it
seems more natural).
--
Tatsuo Ishii
SRA OSS, Inc. Japan

> I would like to propose new large object client side API for 8.4.
>
> Currently we have:
>
>       Oid lo_import(PGconn *conn, const char *filename);
>
> But we do not have an API which imports a large object specifying the
> object id. This is inconvenient and inconsistent since we already have
> lo_create() and lo_open() which allow to specify the large object id.
>
> So I propose to add new API:
>
>       int lo_import_with_oid(PGconn *conn, Oid lobjId, const char *filename);
>
> Another idea is changing the signature of lo_import:
>
>       Oid lo_import(PGconn *conn, Oid lobjId, const char *filename);
>
> which will be cleaner but break the backward compatibility.
>
> Comments are welcome.
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
>
> --
> Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
> To make changes to your subscription:
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? src/interfaces/libpq/exports.list
? src/interfaces/libpq/libpq.so.5.2
Index: doc/src/sgml/lobj.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/lobj.sgml,v
retrieving revision 1.46
diff -c -r1.46 lobj.sgml
*** doc/src/sgml/lobj.sgml    14 Mar 2007 00:15:26 -0000    1.46
--- doc/src/sgml/lobj.sgml    18 Mar 2008 01:02:10 -0000
***************
*** 161,166 ****
--- 161,188 ----
       the server; so it must exist in the client file system and be readable
       by the client application.
      </para>
+
+     <para>
+      The function
+ <synopsis>
+ Oid lo_import_with_oid(PGconn *conn, const char *filename, Oid lobjId);
+ </synopsis>
+      <indexterm><primary>lo_import_with_oid</></>
+      also imports a new large object.  The OID to be assigned can be
+      specified by <replaceable class="parameter">lobjId</replaceable>;
+      if so, failure occurs if that OID is already in use for some large
+      object.  If <replaceable class="parameter">lobjId</replaceable>
+      is <symbol>InvalidOid</symbol> (zero) then <function>lo_import_with_oid</> assigns an unused
+      OID (this is the same behavior as <function>lo_import</>).
+      The return value is the OID that was assigned to the new large object,
+      or <symbol>InvalidOid</symbol> (zero) on failure.
+     </para>
+
+     <para>
+      <function>lo_import_with_oid</> is new as of <productname>PostgreSQL</productname>
+      8.4 and uses <function>lo_create</function> internally which is new in 8.1; if this function is run against 8.0
orbefore, it will 
+      fail and return <symbol>InvalidOid</symbol>.
+     </para>
     </sect2>

     <sect2>
Index: src/interfaces/libpq/exports.txt
===================================================================
RCS file: /cvsroot/pgsql/src/interfaces/libpq/exports.txt,v
retrieving revision 1.18
diff -c -r1.18 exports.txt
*** src/interfaces/libpq/exports.txt    9 Dec 2007 19:01:40 -0000    1.18
--- src/interfaces/libpq/exports.txt    18 Mar 2008 01:02:10 -0000
***************
*** 140,142 ****
--- 140,143 ----
  PQconnectionUsedPassword  138
  pg_valid_server_encoding_id 139
  PQconnectionNeedsPassword 140
+ lo_import_with_oid          141
Index: src/interfaces/libpq/fe-lobj.c
===================================================================
RCS file: /cvsroot/pgsql/src/interfaces/libpq/fe-lobj.c,v
retrieving revision 1.64
diff -c -r1.64 fe-lobj.c
*** src/interfaces/libpq/fe-lobj.c    1 Jan 2008 19:46:00 -0000    1.64
--- src/interfaces/libpq/fe-lobj.c    18 Mar 2008 01:02:11 -0000
***************
*** 41,46 ****
--- 41,48 ----

  static int    lo_initialize(PGconn *conn);

+ static Oid
+ lo_import_internal(PGconn *conn, const char *filename, const Oid oid);

  /*
   * lo_open
***************
*** 484,489 ****
--- 486,512 ----
  Oid
  lo_import(PGconn *conn, const char *filename)
  {
+     return lo_import_internal(conn, filename, InvalidOid);
+ }
+
+ /*
+  * lo_import_with_oid -
+  *      imports a file as an (inversion) large object.
+  *      large object id can be specified.
+  *
+  * returns the oid of that object upon success,
+  * returns InvalidOid upon failure
+  */
+
+ Oid
+ lo_import_with_oid(PGconn *conn, const char *filename, Oid lobjId)
+ {
+     return lo_import_internal(conn, filename, lobjId);
+ }
+
+ static Oid
+ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
+ {
      int            fd;
      int            nbytes,
                  tmp;
***************
*** 507,516 ****
      /*
       * create an inversion object
       */
!     lobjOid = lo_creat(conn, INV_READ | INV_WRITE);
      if (lobjOid == InvalidOid)
      {
!         /* we assume lo_creat() already set a suitable error message */
          (void) close(fd);
          return InvalidOid;
      }
--- 530,543 ----
      /*
       * create an inversion object
       */
!     if (oid == InvalidOid)
!         lobjOid = lo_creat(conn, INV_READ | INV_WRITE);
!     else
!         lobjOid = lo_create(conn, oid);
!
      if (lobjOid == InvalidOid)
      {
!         /* we assume lo_create() already set a suitable error message */
          (void) close(fd);
          return InvalidOid;
      }
Index: src/interfaces/libpq/libpq-fe.h
===================================================================
RCS file: /cvsroot/pgsql/src/interfaces/libpq/libpq-fe.h,v
retrieving revision 1.141
diff -c -r1.141 libpq-fe.h
*** src/interfaces/libpq/libpq-fe.h    1 Jan 2008 19:46:00 -0000    1.141
--- src/interfaces/libpq/libpq-fe.h    18 Mar 2008 01:02:12 -0000
***************
*** 495,500 ****
--- 495,501 ----
  extern int    lo_truncate(PGconn *conn, int fd, size_t len);
  extern int    lo_unlink(PGconn *conn, Oid lobjId);
  extern Oid    lo_import(PGconn *conn, const char *filename);
+ extern Oid    lo_import_with_oid(PGconn *conn, const char *filename, Oid lobjId);
  extern int    lo_export(PGconn *conn, Oid lobjId, const char *filename);

  /* === in fe-misc.c === */