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Add lo_truncate() to backend and libpq for large object truncation.

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Kris Jurka
This commit is contained in:
Bruce Momjian
2007-03-03 19:52:47 +00:00
parent 90d76525c5
commit 0763a56501
12 changed files with 372 additions and 26 deletions
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60
src/interfaces/libpq/fe-lobj.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/interfaces/libpq/fe-lobj.c,v 1.61 2007/01/05 22:20:01 momjian Exp $
* $PostgreSQL: pgsql/src/interfaces/libpq/fe-lobj.c,v 1.62 2007/03/03 19:52:46 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -122,6 +122,59 @@ lo_close(PGconn *conn, int fd)
}
}
/*
* lo_truncate
* truncates an existing large object to the given size
*
* returns 0 upon success
* returns -1 upon failure
*/
int
lo_truncate(PGconn *conn, int fd, size_t len)
{
PQArgBlock argv[2];
PGresult *res;
int retval;
int result_len;
if (conn->lobjfuncs == NULL)
{
if (lo_initialize(conn) < 0)
return -1;
}
/* Must check this on-the-fly because it's not there pre-8.3 */
if (conn->lobjfuncs->fn_lo_truncate == 0)
{
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("cannot determine OID of function lo_truncate\n"));
return -1;
}
argv[0].isint = 1;
argv[0].len = 4;
argv[0].u.integer = fd;
argv[1].isint = 1;
argv[1].len = 4;
argv[1].u.integer = len;
res = PQfn(conn, conn->lobjfuncs->fn_lo_truncate,
&retval, &result_len, 1, argv, 2);
if (PQresultStatus(res) == PGRES_COMMAND_OK)
{
PQclear(res);
return retval;
}
else
{
PQclear(res);
return -1;
}
}
/*
* lo_read
* read len bytes of the large object into buf
@ -621,6 +674,7 @@ lo_initialize(PGconn *conn)
/*
* Execute the query to get all the functions at once. In 7.3 and later
* we need to be schema-safe. lo_create only exists in 8.1 and up.
* lo_truncate only exists in 8.3 and up.
*/
if (conn->sversion >= 70300)
query = "select proname, oid from pg_catalog.pg_proc "
@ -632,6 +686,7 @@ lo_initialize(PGconn *conn)
"'lo_unlink', "
"'lo_lseek', "
"'lo_tell', "
"'lo_truncate', "
"'loread', "
"'lowrite') "
"and pronamespace = (select oid from pg_catalog.pg_namespace "
@ -684,6 +739,8 @@ lo_initialize(PGconn *conn)
lobjfuncs->fn_lo_lseek = foid;
else if (!strcmp(fname, "lo_tell"))
lobjfuncs->fn_lo_tell = foid;
else if (!strcmp(fname, "lo_truncate"))
lobjfuncs->fn_lo_truncate = foid;
else if (!strcmp(fname, "loread"))
lobjfuncs->fn_lo_read = foid;
else if (!strcmp(fname, "lowrite"))
@ -694,7 +751,6 @@ lo_initialize(PGconn *conn)
/*
* Finally check that we really got all large object interface functions
* --- except lo_create, which may not exist.
*/
if (lobjfuncs->fn_lo_open == 0)
{