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Add missing_ok option to the SQL functions for reading files.

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This makes it possible to use the functions without getting errors, if there
is a chance that the file might be removed or renamed concurrently.
pg_rewind needs to do just that, although this could be useful for other
purposes too. (The changes to pg_rewind to use these functions will come in
a separate commit.)

The read_binary_file() function isn't very well-suited for extensions.c's
purposes anymore, if it ever was. So bite the bullet and make a copy of it
in extension.c, tailored for that use case. This seems better than the
accidental code reuse, even if it's a some more lines of code.

Michael Paquier, with plenty of kibitzing by me.
This commit is contained in:
Heikki Linnakangas
2015-06-28 21:35:46 +03:00
parent cca8ba9529
commit cb2acb1081
6 changed files with 274 additions and 102 deletions
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241
src/backend/utils/adt/genfile.c
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@ -35,6 +35,7 @@ typedef struct
{
char *location;
DIR *dirdesc;
bool include_dot_dirs;
} directory_fctx;
@ -87,8 +88,9 @@ convert_and_check_filename(text *arg)
*
* We read the whole of the file when bytes_to_read is negative.
*/
bytea *
read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read)
static bytea *
read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read,
bool missing_ok)
{
bytea *buf;
size_t nbytes;
@ -103,9 +105,14 @@ read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read)
struct stat fst;
if (stat(filename, &fst) < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m", filename)));
{
if (missing_ok && errno == ENOENT)
return NULL;
else
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m", filename)));
}
bytes_to_read = fst.st_size - seek_offset;
}
@ -118,10 +125,15 @@ read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read)
errmsg("requested length too large")));
if ((file = AllocateFile(filename, PG_BINARY_R)) == NULL)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\" for reading: %m",
filename)));
{
if (missing_ok && errno == ENOENT)
return NULL;
else
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\" for reading: %m",
filename)));
}
if (fseeko(file, (off_t) seek_offset,
(seek_offset >= 0) ? SEEK_SET : SEEK_END) != 0)
@ -150,17 +162,23 @@ read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read)
* in the database encoding.
*/
static text *
read_text_file(const char *filename, int64 seek_offset, int64 bytes_to_read)
read_text_file(const char *filename, int64 seek_offset, int64 bytes_to_read,
bool missing_ok)
{
bytea *buf;
buf = read_binary_file(filename, seek_offset, bytes_to_read);
buf = read_binary_file(filename, seek_offset, bytes_to_read, missing_ok);
/* Make sure the input is valid */
pg_verifymbstr(VARDATA(buf), VARSIZE(buf) - VARHDRSZ, false);
if (buf != NULL)
{
/* Make sure the input is valid */
pg_verifymbstr(VARDATA(buf), VARSIZE(buf) - VARHDRSZ, false);
/* OK, we can cast it to text safely */
return (text *) buf;
/* OK, we can cast it to text safely */
return (text *) buf;
}
else
return NULL;
}
/*
@ -170,42 +188,38 @@ Datum
pg_read_file(PG_FUNCTION_ARGS)
{
text *filename_t = PG_GETARG_TEXT_P(0);
int64 seek_offset = PG_GETARG_INT64(1);
int64 bytes_to_read = PG_GETARG_INT64(2);
int64 seek_offset = 0;
int64 bytes_to_read = -1;
bool missing_ok = false;
char *filename;
text *result;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
(errmsg("must be superuser to read files"))));
filename = convert_and_check_filename(filename_t);
/* handle optional arguments */
if (PG_NARGS() >= 3)
{
seek_offset = PG_GETARG_INT64(1);
bytes_to_read = PG_GETARG_INT64(2);
if (bytes_to_read < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("requested length cannot be negative")));
PG_RETURN_TEXT_P(read_text_file(filename, seek_offset, bytes_to_read));
}
/*
* Read the whole of a file, returning it as text
*/
Datum
pg_read_file_all(PG_FUNCTION_ARGS)
{
text *filename_t = PG_GETARG_TEXT_P(0);
char *filename;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
(errmsg("must be superuser to read files"))));
if (bytes_to_read < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("requested length cannot be negative")));
}
if (PG_NARGS() >= 4)
missing_ok = PG_GETARG_BOOL(3);
filename = convert_and_check_filename(filename_t);
PG_RETURN_TEXT_P(read_text_file(filename, 0, -1));
result = read_text_file(filename, seek_offset, bytes_to_read, missing_ok);
if (result)
PG_RETURN_TEXT_P(result);
else
PG_RETURN_NULL();
}
/*
@ -215,42 +229,72 @@ Datum
pg_read_binary_file(PG_FUNCTION_ARGS)
{
text *filename_t = PG_GETARG_TEXT_P(0);
int64 seek_offset = PG_GETARG_INT64(1);
int64 bytes_to_read = PG_GETARG_INT64(2);
int64 seek_offset = 0;
int64 bytes_to_read = -1;
bool missing_ok = false;
char *filename;
bytea *result;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
(errmsg("must be superuser to read files"))));
/* handle optional arguments */
if (PG_NARGS() >= 3)
{
seek_offset = PG_GETARG_INT64(1);
bytes_to_read = PG_GETARG_INT64(2);
if (bytes_to_read < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("requested length cannot be negative")));
}
if (PG_NARGS() >= 4)
missing_ok = PG_GETARG_BOOL(3);
filename = convert_and_check_filename(filename_t);
if (bytes_to_read < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("requested length cannot be negative")));
PG_RETURN_BYTEA_P(read_binary_file(filename, seek_offset, bytes_to_read));
result = read_binary_file(filename, seek_offset,
bytes_to_read, missing_ok);
if (result)
PG_RETURN_BYTEA_P(result);
else
PG_RETURN_NULL();
}
/*
* Read the whole of a file, returning it as bytea
* Wrapper functions for the 1 and 3 argument variants of pg_read_file()
* and pg_binary_read_file().
*
* These are necessary to pass the sanity check in opr_sanity, which checks
* that all built-in functions that share the implementing C function take
* the same number of arguments.
*/
Datum
pg_read_file_off_len(PG_FUNCTION_ARGS)
{
return pg_read_file(fcinfo);
}
Datum
pg_read_file_all(PG_FUNCTION_ARGS)
{
return pg_read_file(fcinfo);
}
Datum
pg_read_binary_file_off_len(PG_FUNCTION_ARGS)
{
return pg_read_binary_file(fcinfo);
}
Datum
pg_read_binary_file_all(PG_FUNCTION_ARGS)
{
text *filename_t = PG_GETARG_TEXT_P(0);
char *filename;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
(errmsg("must be superuser to read files"))));
filename = convert_and_check_filename(filename_t);
PG_RETURN_BYTEA_P(read_binary_file(filename, 0, -1));
return pg_read_binary_file(fcinfo);
}
/*
@ -266,18 +310,28 @@ pg_stat_file(PG_FUNCTION_ARGS)
bool isnull[6];
HeapTuple tuple;
TupleDesc tupdesc;
bool missing_ok = false;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
(errmsg("must be superuser to get file information"))));
/* check the optional argument */
if (PG_NARGS() == 2)
missing_ok = PG_GETARG_BOOL(1);
filename = convert_and_check_filename(filename_t);
if (stat(filename, &fst) < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m", filename)));
{
if (missing_ok && errno == ENOENT)
PG_RETURN_NULL();
else
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m", filename)));
}
/*
* This record type had better match the output parameters declared for me
@ -320,6 +374,18 @@ pg_stat_file(PG_FUNCTION_ARGS)
PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
}
/*
* stat a file (1 argument version)
*
* note: this wrapper is necessary to pass the sanity check in opr_sanity,
* which checks that all built-in functions that share the implementing C
* function take the same number of arguments
*/
Datum
pg_stat_file_1arg(PG_FUNCTION_ARGS)
{
return pg_stat_file(fcinfo);
}
/*
* List a directory (returns the filenames only)
@ -330,6 +396,7 @@ pg_ls_dir(PG_FUNCTION_ARGS)
FuncCallContext *funcctx;
struct dirent *de;
directory_fctx *fctx;
MemoryContext oldcontext;
if (!superuser())
ereport(ERROR,
@ -338,7 +405,17 @@ pg_ls_dir(PG_FUNCTION_ARGS)
if (SRF_IS_FIRSTCALL())
{
MemoryContext oldcontext;
bool missing_ok = false;
bool include_dot_dirs = false;
/* check the optional arguments */
if (PG_NARGS() == 3)
{
if (!PG_ARGISNULL(1))
missing_ok = PG_GETARG_BOOL(1);
if (!PG_ARGISNULL(2))
include_dot_dirs = PG_GETARG_BOOL(2);
}
funcctx = SRF_FIRSTCALL_INIT();
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
@ -346,14 +423,22 @@ pg_ls_dir(PG_FUNCTION_ARGS)
fctx = palloc(sizeof(directory_fctx));
fctx->location = convert_and_check_filename(PG_GETARG_TEXT_P(0));
fctx->include_dot_dirs = include_dot_dirs;
fctx->dirdesc = AllocateDir(fctx->location);
if (!fctx->dirdesc)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open directory \"%s\": %m",
fctx->location)));
{
if (missing_ok && errno == ENOENT)
{
MemoryContextSwitchTo(oldcontext);
SRF_RETURN_DONE(funcctx);
}
else
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open directory \"%s\": %m",
fctx->location)));
}
funcctx->user_fctx = fctx;
MemoryContextSwitchTo(oldcontext);
}
@ -363,8 +448,9 @@ pg_ls_dir(PG_FUNCTION_ARGS)
while ((de = ReadDir(fctx->dirdesc, fctx->location)) != NULL)
{
if (strcmp(de->d_name, ".") == 0 ||
strcmp(de->d_name, "..") == 0)
if (!fctx->include_dot_dirs &&
(strcmp(de->d_name, ".") == 0 ||
strcmp(de->d_name, "..") == 0))
continue;
SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(de->d_name));
@ -374,3 +460,16 @@ pg_ls_dir(PG_FUNCTION_ARGS)
SRF_RETURN_DONE(funcctx);
}
/*
* List a directory (1 argument version)
*
* note: this wrapper is necessary to pass the sanity check in opr_sanity,
* which checks that all built-in functions that share the implementing C
* function take the same number of arguments.
*/
Datum
pg_ls_dir_1arg(PG_FUNCTION_ARGS)
{
return pg_ls_dir(fcinfo);
}