Harald,
Friday, August 16, 2002, 5:46:20 PM, you wrote:
HF> In article <[EMAIL PROTECTED]>,
HF> Victoria Reznichenko <[EMAIL PROTECTED]> writes:
>> Harald,
>> Thursday, August 15, 2002, 4:02:44 PM, you wrote:
[skip]
HF>> According to the manual, LOAD_FILE returns NULL if the file is too
HF>> large, but apparently this isn't the case here.
>> In your case total text length is bigger than max_allowed_packet, that
>> is why you've got len=0
HF> Victoria,
HF> I agree that this must be the case, but it is contrary to what the
HF> manual says:
HF> `LOAD_FILE(file_name)'
HF> Reads the file and returns the file contents as a string. The file
HF> must be on the server, you must specify the full pathname to the
HF> file, and you must have the `FILE' privilege. The file must be
HF> readable by all and be smaller than `max_allowed_packet'.
HF> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
HF> If the file doesn't exist or can't be read due to one of the above
HF> reasons, the function returns `NULL': ...
HF> The manual states clearly that _the file_ must be smaller than
HF> max_allowed_packet (which it is), *not* the total text length.
Harald, LOAD_FILE() doesn't play any role in this query. You got NULL
not because of LOAD_FILE().
Look:
CREATE TABLE `tbl1` (
`id` tinyint(3) unsigned NOT NULL auto_increment,
`txt1` longtext NOT NULL,
`txt2` longtext NOT NULL,
`total` longtext NOT NULL,
PRIMARY KEY (`id`)
) TYPE=MyISAM
INSERT INTO tbl1(txt1, txt2) VALUES (LOAD_FILE('/home/greta/mtest1.txt'),
LOAD_FILE('/home/greta/mtest1.txt'));
SELECT id, LENGTH(txt1), LENGTH(txt2), LENGTH(total) FROM tbl1;
+----+--------------+--------------+---------------+
| id | LENGTH(txt1) | LENGTH(txt2) | LENGTH(total) |
+----+--------------+--------------+---------------+
| 1 | 8390060 | 8390060 | 0 |
+----+--------------+--------------+---------------+
As you can see txt1 and txt2 contain text file ~ 8M
UPDATE tbl1 SET total=CONCAT(txt1,txt2) WHERE id=1;
SELECT id, LENGTH(txt1), LENGTH(txt2), LENGTH(total) FROM tbl1;
+----+--------------+--------------+---------------+
| id | LENGTH(txt1) | LENGTH(txt2) | LENGTH(total) |
+----+--------------+--------------+---------------+
| 1 | 8390060 | 8390060 | 0 |
+----+--------------+--------------+---------------+
The same result.
MySQL inserts NULL in the total, because you can't store data more
than max_allowed_packet.
HF> I think this behaviour is highly unintuitive - after all, I don't
HF> transfer more than max_allowed_packet bytes to the server.
HF> So I'd suggest that this should be documented in the manual.
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