Re: [Sqlalchemy-tickets] [sqlalchemy] #2843: Support for IF EXISTS/IF NOT EXISTS DDL constructs

[sqlalchemy <mi...@zz...>]

#2843: Support for IF EXISTS/IF NOT EXISTS DDL constructs
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      Reporter:  remyroy      |      Owner:  zzzeek
          Type:  enhancement  |     Status:  new
      Priority:  medium       |  Milestone:  0.9.xx
     Component:  schema       |   Severity:  major - 1-3 hours
    Resolution:               |   Keywords:
Progress State:  in queue     |
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Comment (by zzzeek):

 well the downside is that different database backends would now take an
 entirely different approach for create/drop, which would remove a certain
 consistency of approach we've had for many years in this area, as well as
 place a new and unproven feature at the center of a very stable and
 critical function.   if performance is a concern (which it's generally
 not) I was thinking we could instead amend dialects to include a new
 "has_tables" function, that could query the existence of many tables all
 at once, providing a performance improvement that applies to any backend
 (at least as long as they support querying for multiple table names at
 once via system views).   the case where most tables exist already would
 otherwise mean there'd be a lot of fully rendered CREATE TABLE statements
 being parsed for no reason.

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2843#comment:4>
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