Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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5.5.47-galera
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Centos 7
Description
Using SELECT INTO local routine variable, value is assigned to two distinct variables.
Test cast to reproduce issue;
Two tables with one row with different values
CREATE TABLE `test`.`A`(
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`idA` BIGINT NOT NULL AUTO_INCREMENT,
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`messageA` MEDIUMBLOB,
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PRIMARY KEY (`idA`)
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);
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CREATE TABLE `test`.`B`(
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`idB` BIGINT NOT NULL AUTO_INCREMENT,
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`messageB` MEDIUMBLOB,
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PRIMARY KEY (`idB`)
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);
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INSERT INTO A(messageA) VALUES (COMPRESS('messageA')); |
INSERT INTO B(messageB) VALUES (COMPRESS('messageB')); |
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Stored procedure:
DELIMITER $$
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CREATE PROCEDURE `procC`()
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BEGIN
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DECLARE pA MEDIUMBLOB;
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DECLARE pB MEDIUMBLOB;
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SElect messageA
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into pA
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FROM A;
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SELECT messageB
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into pB
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from B;
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select UNCOMPRESS(pA), UNCOMPRESS(pB);
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END$$
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DELIMITER ;
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Calling procedure:
CALL procC();
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Expected result:
messageA, messageB
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Result:
messageB, messageB
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The bug was fixed in 5.5.48 by the following commit (merged from upstream):
commit 863f7cebd79e76f90bd8f1e3e0c1a1de5fe77d07 3d1306f7b74077cfa197c8fa23baeb96c535af67Author: Sreeharsha Ramanavarapu <sreeharsha.ramanavarapu@oracle.com>Date: Fri Jan 8 06:46:59 2016 +0530Bug #22232332: SAVING TEXT FIELD TO TEXT VARIABLE IN APROCEDURE RESULTS IN GARBAGE BYTESIssue:-----This problem occurs under the following conditions:a) Stored procedure has a variable is declared as TEXT/BLOB.b) Data is copied into the the variable using theSELECT...INTO syntax from a TEXT/BLOB column.Data corruption can occur in such cases.SOLUTION:---------The blob type does not allocate space for the string to bestored. Instead it contains a pointer to the source string.Since the source is deallocated immediately after theselect statement, this can cause data corruption.As part of the fix for Bug #21143080, when the source waspart of the table's write-set, blob would allocate theneccessary space. But this fix missed the possibility that,as in the above case, the target might be a variable.The fix will add the copy_blobs check that was removed bythe earlier fix.