[Phplib-trackers] [ phplib-Bugs-542808 ] nextid()'s lock() in db_mysql.inc

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Bugs item #542808, was opened at 2002-04-11 22:15
You can respond by visiting: 
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Category: DB_SQL
Group: current CVS
Status: Open
Resolution: None
Priority: 5
Submitted By: Layne Weathers (layne_weathers)
Assigned to: Nobody/Anonymous (nobody)
Summary: nextid()'s lock() in db_mysql.inc

Initial Comment:
nextid() issues a table lock on the db_sequence table -
 this will release any previous locks. I do not 
believe that nextid() is competent to make that 
decision on its own. In most applications, I lock 
tables before modifying any data, do integrity and 
validity tests on the new data, and finally make the 
changes. Since I don't like throwing away auto-
incrementing ID #s, I don't call nextid() until right 
before the insert statement. Unfortunately, nextid() 
will release my other locks and compromise my efforts 
at data integrity.

If my methodology above is flawed I am willing to 
change it, but until persuaded otherwise I propose the 
following order for nextid(): 

1. check to see if an instance-level lock is in place
  1.1. if not, try to put a lock on the sequence table
      1.1.1. if successful, record that a local lock 
was used
      1.1.2. if unsuccessful, fail with current warning

2. get current id, increment it, write it to table 
(unmodified)

3. check for a local lock
  3.1 if so, release it


(Yes, this will cause problems in existing code where 
nextid() is used within a set of locked tables and the 
sequence table was not locked - the author was sloppy 
and overlooked the sequence table, s/he should fix the 
code.)

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