Re: AUTO_PK_SUPPORT optimization

From: Gili (cowwo..bs.darktech.org)
Date: Fri Sep 09 2005 - 17:01:30 EDT

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            On a related note, note how we update the exact same row three times
    (and acquire locks three times). Cayenne could group these calls into a
    single call... (The log that follows results from a single
    commitChanges() call).

    16:55:45,062 INFO QueryLogger:315 - LOCK TABLES AUTO_PK_SUPPORT WRITE
    16:55:45,062 INFO QueryLogger:315 - SELECT NEXT_ID FROM AUTO_PK_SUPPORT
    WHERE TABLE_NAME = 'image'
    16:55:45,078 INFO QueryLogger:315 - UPDATE AUTO_PK_SUPPORT SET NEXT_ID
    = NEXT_ID + 20 WHERE TABLE_NAME = 'image' AND NEXT_ID = 3580
    16:55:45,078 INFO QueryLogger:315 - UNLOCK TABLES
    16:55:45,078 INFO QueryLogger:315 - LOCK TABLES AUTO_PK_SUPPORT WRITE
    16:55:45,078 INFO QueryLogger:315 - SELECT NEXT_ID FROM AUTO_PK_SUPPORT
    WHERE TABLE_NAME = 'image'
    16:55:45,078 INFO QueryLogger:315 - UPDATE AUTO_PK_SUPPORT SET NEXT_ID
    = NEXT_ID + 20 WHERE TABLE_NAME = 'image' AND NEXT_ID = 3600
    16:55:45,078 INFO QueryLogger:315 - UNLOCK TABLES
    16:55:45,078 INFO QueryLogger:315 - LOCK TABLES AUTO_PK_SUPPORT WRITE
    16:55:45,093 INFO QueryLogger:315 - SELECT NEXT_ID FROM AUTO_PK_SUPPORT
    WHERE TABLE_NAME = 'image'
    16:55:45,093 INFO QueryLogger:315 - UPDATE AUTO_PK_SUPPORT SET NEXT_ID
    = NEXT_ID + 20 WHERE TABLE_NAME = 'image' AND NEXT_ID = 3620
    16:55:45,093 INFO QueryLogger:315 - UNLOCK TABLES

    Gili

    Gili wrote:
    >
    > Under MySQL, when we use AUTO_PK_SUPPORT we pessimistically lock the
    > table as well as using optimistic locking. We should be doing one, not
    > both. Do you guys see the same thing under other DBs?
    >
    > Gili 

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