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In case when filesort does not use addon field packing (because of too small potential savings) and uses fixed width addon fields instead, the field->pack() call can store less bytes when the field maximum possible field length, e.g. in case of VARCHAR(). The memory between the packed length and addonf->length (the maximum length) stayed uninitialized, which was reported by Valgrind/MSAN. The problem was introduced byf52bf92014in 10.5, which removed the tail initialization (probably unintentionally). Restoring the bzero() in the fixed length branch, so in case when pack() stores less bytes than addonf->length says, the trailing bytes gets initialized. Note, beforef52bf92014, the bzero() was under HAVE_valgrind conditional compilation. Now it's being added unconditionally: - MSAN also reported the problem, so it's not only Valgrind specific. - As Serg proposed, conditional initialization is bad - it can have potentional security problems as the non-initialized memory fragments can store various pieces of essential information, e.g. passwords.
51 lines
1.1 KiB
Text
51 lines
1.1 KiB
Text
#
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# Tests related to pack modes of the sortkey and addon fields.
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# Fields can be either packed or fixed length.
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#
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# See the comment in filesort.cc:
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#
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# Heuristic: skip packing if potential savings are less than 10 bytes.
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#
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--echo #
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--echo # Start of 10.5 tests
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--echo #
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--echo #
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--echo # MDEV-27307 main.ctype_utf8mb4_uca_allkeys tests fail with Valgrind/MSAN
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--echo #
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--echo # In this scenario packing is fully disabled:
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--echo # - The sortkey is of a fixed width data type
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--echo # - The addon fields have too small potential savings
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SET NAMES latin1;
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CREATE TABLE t1 (
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code INT NOT NULL,
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str VARCHAR(5) CHARACTER SET latin1 NOT NULL
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) ENGINE=MyISAM;
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DELIMITER $$;
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FOR i IN 0..50
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DO
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INSERT INTO t1 VALUES (i, REPEAT('a',1));
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END FOR;
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$$
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DELIMITER ;$$
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SELECT COUNT(*) FROM t1;
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# The result is not very interesting, let's suppress it.
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# We just make sure there are no Valgrind/MSAN warnings about
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# not initialized memory being written to disk.
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SET sort_buffer_size=1024;
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--disable_result_log
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SELECT HEX(code), HEX(str) FROM t1 ORDER BY HEX(str);
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--enable_result_log
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SET sort_buffer_size=DEFAULT;
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DROP TABLE t1;
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--echo #
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--echo # End of 10.5 tests
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--echo #
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