Improve error detection and recovery in lo_import()/lo_export().

Problems noted while experimenting with new control-C code for psql.

diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 5d81a6ea3391d6f4ad55fa226d2a47354c4fae18..5e11b0e3059bd857efd409d5f1adba1547d85f10 100644 (file)
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/interfaces/libpq/fe-lobj.c,v 1.56 2006/03/05 15:59:09 momjian Exp $
+ *   $PostgreSQL: pgsql/src/interfaces/libpq/fe-lobj.c,v 1.57 2006/06/14 01:28:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -58,6 +58,12 @@ lo_open(PGconn *conn, Oid lobjId, int mode)
    PQArgBlock  argv[2];
    PGresult   *res;
 
+   if (conn->lobjfuncs == NULL)
+   {
+       if (lo_initialize(conn) < 0)
+           return -1;
+   }
+
    argv[0].isint = 1;
    argv[0].len = 4;
    argv[0].u.integer = lobjId;
@@ -66,12 +72,6 @@ lo_open(PGconn *conn, Oid lobjId, int mode)
    argv[1].len = 4;
    argv[1].u.integer = mode;
 
-   if (conn->lobjfuncs == NULL)
-   {
-       if (lo_initialize(conn) < 0)
-           return -1;
-   }
-
    res = PQfn(conn, conn->lobjfuncs->fn_lo_open, &fd, &result_len, 1, argv, 2);
    if (PQresultStatus(res) == PGRES_COMMAND_OK)
    {
@@ -438,6 +438,7 @@ lo_import(PGconn *conn, const char *filename)
    char        buf[LO_BUFSIZE];
    Oid         lobjOid;
    int         lobj;
+   char        sebuf[256];
 
    /*
     * open the file to be read in
@@ -445,8 +446,6 @@ lo_import(PGconn *conn, const char *filename)
    fd = open(filename, O_RDONLY | PG_BINARY, 0666);
    if (fd < 0)
    {                           /* error */
-       char        sebuf[256];
-
        printfPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("could not open file \"%s\": %s\n"),
                          filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
@@ -454,7 +453,7 @@ lo_import(PGconn *conn, const char *filename)
    }
 
    /*
-    * create an inversion "object"
+    * create an inversion object
     */
    lobjOid = lo_creat(conn, INV_READ | INV_WRITE);
    if (lobjOid == InvalidOid)
@@ -477,24 +476,46 @@ lo_import(PGconn *conn, const char *filename)
    }
 
    /*
-    * read in from the Unix file and write to the inversion file
+    * read in from the file and write to the large object
     */
    while ((nbytes = read(fd, buf, LO_BUFSIZE)) > 0)
    {
        tmp = lo_write(conn, lobj, buf, nbytes);
-       if (tmp < nbytes)
+       if (tmp != nbytes)
        {
+           /*
+            * If the lo_write failed, we are probably in an aborted
+            * transaction and so lo_close will fail.  Try it anyway for
+            * cleanliness, but don't let it determine the returned error
+            * message.
+            */
+           (void) lo_close(conn, lobj);
+
            printfPQExpBuffer(&conn->errorMessage,
-                         libpq_gettext("error while reading file \"%s\"\n"),
-                             filename);
+                       libpq_gettext("error while writing large object %u\n"),
+                             lobjOid);
            (void) close(fd);
-           (void) lo_close(conn, lobj);
            return InvalidOid;
        }
    }
 
+   if (nbytes < 0)
+   {
+       printfPQExpBuffer(&conn->errorMessage,
+                       libpq_gettext("could not read from file \"%s\": %s\n"),
+                         filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
+       lobjOid = InvalidOid;
+   }
+
    (void) close(fd);
-   (void) lo_close(conn, lobj);
+
+   if (lo_close(conn, lobj) != 0)
+   {
+       printfPQExpBuffer(&conn->errorMessage,
+                       libpq_gettext("error while writing large object %u\n"),
+                         lobjOid);
+       return InvalidOid;
+   }
 
    return lobjOid;
 }
@@ -502,16 +523,18 @@ lo_import(PGconn *conn, const char *filename)
 /*
  * lo_export -
  *   exports an (inversion) large object.
- * returns -1 upon failure, 1 otherwise
+ * returns -1 upon failure, 1 if OK
  */
 int
 lo_export(PGconn *conn, Oid lobjId, const char *filename)
 {
+   int         result = 1;
    int         fd;
    int         nbytes,
                tmp;
    char        buf[LO_BUFSIZE];
    int         lobj;
+   char        sebuf[256];
 
    /*
     * open the large object.
@@ -530,8 +553,6 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
    fd = open(filename, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY, 0666);
    if (fd < 0)
    {                           /* error */
-       char        sebuf[256];
-
        printfPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("could not open file \"%s\": %s\n"),
                          filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
@@ -540,33 +561,39 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
    }
 
    /*
-    * read in from the inversion file and write to the Unix file
+    * read in from the large object and write to the file
     */
    while ((nbytes = lo_read(conn, lobj, buf, LO_BUFSIZE)) > 0)
    {
        tmp = write(fd, buf, nbytes);
-       if (tmp < nbytes)
+       if (tmp != nbytes)
        {
            printfPQExpBuffer(&conn->errorMessage,
-                      libpq_gettext("error while writing to file \"%s\"\n"),
-                             filename);
+                      libpq_gettext("error while writing to file \"%s\": %s\n"),
+                         filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
            (void) lo_close(conn, lobj);
            (void) close(fd);
            return -1;
        }
    }
 
-   (void) lo_close(conn, lobj);
+   if (lo_close(conn, lobj) != 0 || nbytes < 0)
+   {
+       printfPQExpBuffer(&conn->errorMessage,
+                       libpq_gettext("error while reading large object %u\n"),
+                         lobjId);
+       result = -1;
+   }
 
    if (close(fd))
    {
        printfPQExpBuffer(&conn->errorMessage,
-                      libpq_gettext("error while writing to file \"%s\"\n"),
-                         filename);
-       return -1;
+                      libpq_gettext("error while writing to file \"%s\": %s\n"),
+                         filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
+       result = -1;
    }
 
-   return 1;
+   return result;
 }