[sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Kent]

Along the same lines, is there something we can do about nvl()
(oracle) versus coalesce() (ansi)?

They aren't exactly the same, unfortunately (nvl takes exactly 2
arguments, no more), so maybe there is nothing 'official' you can do,
but can you help me work it out for my project?

I assume it is very similar to what you helped me out with
above...something like this:


from sqlalchemy.sql.expression import ColumnElement
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.types import DateTime, Date

class current_date(ColumnElement):
type = Date()

@compiles(current_date)
def _compiler_dispatch(element, compiler, **kw):
if compiler.dialect.name == 'oracle':
if compiler.dialect.use_ansi:
return trunc(current_date)
else:
return trunc(sysdate)
else:
# assume postgres
return current_date



But the main difference is it takes arguments.

Is there a clever way to return the appropriate function, something
like this:

def 
if compiler.dialect.name == 'oracle':
return func.nvl
else:
# assume postgres
return func.coalesce


How would I work that out?


Thank you in advance.



On Apr 2, 4:12 pm, Michael Bayer mike...@zzzcomputing.com wrote:
 Kent wrote:
  Any chance you plan to make func.now consider oracle and
  use_ansi=False (and return sysdate)?

 the use_ansi flag should be removed as far as public API since we can
 detect server version now.   we can also make now() return sysdate()
 unconditionally on oracle, you should give us a trac ticket for the latter
 on milestone 0.6.



  On Feb 3, 4:44 pm, Michael Bayer mike...@zzzcomputing.com wrote:
  Kent wrote:
   Any chance SQLAlchemy has a mechanism to switch to or fromsysdatevs.
  current_datebased on the database dialect (and maybe use_ansi)?

   It would be really nice if I could program in sqla not knowing which
   database type I am connected to and still could select the current
   date from the database... can I?

  func.now() does do this (well, it returns CURRENT_TIMESTAMP,
  isCURRENT_DATEdifferent?). it doesn't take use_ansi into account
  though
  (though that would be an easy patch to theOracledialect).

  Aside from all that, this is also easy enough to roll yourself:

  from sqlalchemy.sql.expression import ColumnElement
  from sqlalchemy.ext.compiler import compiles

  classcurrent_date(ColumnElement):
  type = sa.DateTime()

  @compiler.compiles(current_date)
  def _compiler_dispatch(element, compiler, **kw):
  if compiler.dialect.name == 'oracle':
  if not compiler.dialect.use_ansi:
  return sysdate
  else:
  return current_date
  else:
  # etc ...

  then just saycurrent_date() to get the expression.

  you could also throw @compiles onto sqlalchemy.sql.functions.now if
  you
  wanted to augment what func.now() returns.

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Re: [sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Michael Bayer]

Kent wrote:
 Along the same lines, is there something we can do about nvl()
 (oracle) versus coalesce() (ansi)?

 They aren't exactly the same, unfortunately (nvl takes exactly 2
 arguments, no more), so maybe there is nothing 'official' you can do,
 but can you help me work it out for my project?

 I assume it is very similar to what you helped me out with
 above...something like this:

 
 from sqlalchemy.sql.expression import ColumnElement
 from sqlalchemy.ext.compiler import compiles
 from sqlalchemy.types import DateTime, Date

 class current_date(ColumnElement):
 type = Date()

 @compiles(current_date)
 def _compiler_dispatch(element, compiler, **kw):
 if compiler.dialect.name == 'oracle':
 if compiler.dialect.use_ansi:
 return trunc(current_date)
 else:
 return trunc(sysdate)
 else:
 # assume postgres
 return current_date
 


 But the main difference is it takes arguments.

 Is there a clever way to return the appropriate function, something
 like this:

 def 
 if compiler.dialect.name == 'oracle':
 return func.nvl
 else:
 # assume postgres
 return func.coalesce

I will add this to the docs:


from sqlalchemy import *
from sqlalchemy.ext.compiler import compiles

from sqlalchemy.sql.expression import FunctionElement


class coalesce(FunctionElement):
name = 'coalesce'

@compiles(coalesce)
def compile(element, compiler, **kw):
return coalesce(%s) % compiler.process(element.clauses)


@compiles(coalesce, 'oracle')
def compile(element, compiler, **kw):
if len(element.clauses)  2:
raise TypeError(coalesce only supports two arguments on Oracle)
return nvl(%s) % compiler.process(element.clauses)

print coalesce(5, 6)

from sqlalchemy.dialects import oracle
print coalesce(5, 6).compile(dialect=oracle.dialect())

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Re: [sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Kent Bower]

Thanks very much.

On 4/2/2010 5:41 PM, Michael Bayer wrote:

Kent wrote:
   

Along the same lines, is there something we can do about nvl()
(oracle) versus coalesce() (ansi)?

They aren't exactly the same, unfortunately (nvl takes exactly 2
arguments, no more), so maybe there is nothing 'official' you can do,
but can you help me work it out for my project?

I assume it is very similar to what you helped me out with
above...something like this:


from sqlalchemy.sql.expression import ColumnElement
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.types import DateTime, Date

class current_date(ColumnElement):
 type = Date()

@compiles(current_date)
def _compiler_dispatch(element, compiler, **kw):
 if compiler.dialect.name == 'oracle':
 if compiler.dialect.use_ansi:
 return trunc(current_date)
 else:
 return trunc(sysdate)
 else:
 # assume postgres
 return current_date



But the main difference is it takes arguments.

Is there a clever way to return the appropriate function, something
like this:

def 
 if compiler.dialect.name == 'oracle':
 return func.nvl
 else:
 # assume postgres
 return func.coalesce
 

I will add this to the docs:


from sqlalchemy import *
from sqlalchemy.ext.compiler import compiles

from sqlalchemy.sql.expression import FunctionElement


class coalesce(FunctionElement):
 name = 'coalesce'

@compiles(coalesce)
def compile(element, compiler, **kw):
 return coalesce(%s) % compiler.process(element.clauses)


@compiles(coalesce, 'oracle')
def compile(element, compiler, **kw):
 if len(element.clauses)  2:
 raise TypeError(coalesce only supports two arguments on Oracle)
 return nvl(%s) % compiler.process(element.clauses)

print coalesce(5, 6)

from sqlalchemy.dialects import oracle
print coalesce(5, 6).compile(dialect=oracle.dialect())

   


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Re: [sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Kent Bower]

As an aside, more recent Oracles support ansi coalesce,
so it is probably more appropriate to only use nvl() for older, non-ansi 
Oracle versions, but if this is only for illustration then that is not a 
big deal (unless you don't want people writing to you saying coalesce 
does support more than 2 arguments.


In my case, I'd rather rework the nvl() function to work on other 
engines besides Oracle as an alias to coalesce(), seems less ambiguous.


Thanks again.



On 4/2/2010 5:41 PM, Michael Bayer wrote:

Kent wrote:
   

Along the same lines, is there something we can do about nvl()
(oracle) versus coalesce() (ansi)?

They aren't exactly the same, unfortunately (nvl takes exactly 2
arguments, no more), so maybe there is nothing 'official' you can do,
but can you help me work it out for my project?

I assume it is very similar to what you helped me out with
above...something like this:


from sqlalchemy.sql.expression import ColumnElement
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.types import DateTime, Date

class current_date(ColumnElement):
 type = Date()

@compiles(current_date)
def _compiler_dispatch(element, compiler, **kw):
 if compiler.dialect.name == 'oracle':
 if compiler.dialect.use_ansi:
 return trunc(current_date)
 else:
 return trunc(sysdate)
 else:
 # assume postgres
 return current_date



But the main difference is it takes arguments.

Is there a clever way to return the appropriate function, something
like this:

def 
 if compiler.dialect.name == 'oracle':
 return func.nvl
 else:
 # assume postgres
 return func.coalesce
 

I will add this to the docs:


from sqlalchemy import *
from sqlalchemy.ext.compiler import compiles

from sqlalchemy.sql.expression import FunctionElement


class coalesce(FunctionElement):
 name = 'coalesce'

@compiles(coalesce)
def compile(element, compiler, **kw):
 return coalesce(%s) % compiler.process(element.clauses)


@compiles(coalesce, 'oracle')
def compile(element, compiler, **kw):
 if len(element.clauses)  2:
 raise TypeError(coalesce only supports two arguments on Oracle)
 return nvl(%s) % compiler.process(element.clauses)

print coalesce(5, 6)

from sqlalchemy.dialects import oracle
print coalesce(5, 6).compile(dialect=oracle.dialect())

   


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Re: [sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Michael Bayer]

Kent Bower wrote:
 As an aside, more recent Oracles support ansi coalesce,
 so it is probably more appropriate to only use nvl() for older, non-ansi
 Oracle versions, but if this is only for illustration then that is not a
 big deal (unless you don't want people writing to you saying coalesce
 does support more than 2 arguments.

 In my case, I'd rather rework the nvl() function to work on other
 engines besides Oracle as an alias to coalesce(), seems less ambiguous.

ultimately the oracle dialect should do the same thing we want it to do
for now() here.  return nvl() on oracle 8.


 Thanks again.



 On 4/2/2010 5:41 PM, Michael Bayer wrote:
 Kent wrote:

 Along the same lines, is there something we can do about nvl()
 (oracle) versus coalesce() (ansi)?

 They aren't exactly the same, unfortunately (nvl takes exactly 2
 arguments, no more), so maybe there is nothing 'official' you can do,
 but can you help me work it out for my project?

 I assume it is very similar to what you helped me out with
 above...something like this:

 
 from sqlalchemy.sql.expression import ColumnElement
 from sqlalchemy.ext.compiler import compiles
 from sqlalchemy.types import DateTime, Date

 class current_date(ColumnElement):
  type = Date()

 @compiles(current_date)
 def _compiler_dispatch(element, compiler, **kw):
  if compiler.dialect.name == 'oracle':
  if compiler.dialect.use_ansi:
  return trunc(current_date)
  else:
  return trunc(sysdate)
  else:
  # assume postgres
  return current_date
 


 But the main difference is it takes arguments.

 Is there a clever way to return the appropriate function, something
 like this:

 def 
  if compiler.dialect.name == 'oracle':
  return func.nvl
  else:
  # assume postgres
  return func.coalesce

 I will add this to the docs:


 from sqlalchemy import *
 from sqlalchemy.ext.compiler import compiles

 from sqlalchemy.sql.expression import FunctionElement


 class coalesce(FunctionElement):
  name = 'coalesce'

 @compiles(coalesce)
 def compile(element, compiler, **kw):
  return coalesce(%s) % compiler.process(element.clauses)


 @compiles(coalesce, 'oracle')
 def compile(element, compiler, **kw):
  if len(element.clauses)  2:
  raise TypeError(coalesce only supports two arguments on
 Oracle)
  return nvl(%s) % compiler.process(element.clauses)

 print coalesce(5, 6)

 from sqlalchemy.dialects import oracle
 print coalesce(5, 6).compile(dialect=oracle.dialect())



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Re: [sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Ian Kelly]

On Fri, Apr 2, 2010 at 3:41 PM, Michael Bayer mike...@zzzcomputing.comwrote:

 Kent wrote:
  Along the same lines, is there something we can do about nvl()
  (oracle) versus coalesce() (ansi)?
 
  They aren't exactly the same, unfortunately (nvl takes exactly 2
  arguments, no more), so maybe there is nothing 'official' you can do,
  but can you help me work it out for my project?
 
  I assume it is very similar to what you helped me out with
  above...something like this:
 
  
  from sqlalchemy.sql.expression import ColumnElement
  from sqlalchemy.ext.compiler import compiles
  from sqlalchemy.types import DateTime, Date
 
  class current_date(ColumnElement):
  type = Date()
 
  @compiles(current_date)
  def _compiler_dispatch(element, compiler, **kw):
  if compiler.dialect.name == 'oracle':
  if compiler.dialect.use_ansi:
  return trunc(current_date)
  else:
  return trunc(sysdate)
  else:
  # assume postgres
  return current_date
  
 
 
  But the main difference is it takes arguments.
 
  Is there a clever way to return the appropriate function, something
  like this:
 
  def 
  if compiler.dialect.name == 'oracle':
  return func.nvl
  else:
  # assume postgres
  return func.coalesce

 I will add this to the docs:


 from sqlalchemy import *
 from sqlalchemy.ext.compiler import compiles

 from sqlalchemy.sql.expression import FunctionElement


 class coalesce(FunctionElement):
name = 'coalesce'

 @compiles(coalesce)
 def compile(element, compiler, **kw):
return coalesce(%s) % compiler.process(element.clauses)


 @compiles(coalesce, 'oracle')
 def compile(element, compiler, **kw):
if len(element.clauses)  2:
raise TypeError(coalesce only supports two arguments on Oracle)
return nvl(%s) % compiler.process(element.clauses)

 print coalesce(5, 6)

 from sqlalchemy.dialects import oracle
 print coalesce(5, 6).compile(dialect=oracle.dialect())


Might this work as a more complete solution for Oracle?

@compiles(coalesce, 'oracle')
def compile(element, compiler, **kw):
   sql = nvl(%s)
   for i in xrange(len(element.clauses) - 2):
  sql %= %s, nvl(%%s) % compiler.process(element.clauses[i:i+1])
   return sql % compiler.process(element.clauses[-2:])

Ian

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[sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Kent]

Just to be inconsistent, with one argument, databases handle this
differently:

postgres:
# select coalesce(0);
 coalesce
--
0
(1 row)


Oracle 10g:

select coalesce(0) from dual
   *
ERROR at line 1:
ORA-00938: not enough arguments for function




On Apr 2, 7:08 pm, Ian Kelly ian.g.ke...@gmail.com wrote:
 On Fri, Apr 2, 2010 at 3:41 PM, Michael Bayer mike...@zzzcomputing.comwrote:



  Kent wrote:
   Along the same lines, is there something we can do about nvl()
   (oracle) versus coalesce() (ansi)?

   They aren't exactly the same, unfortunately (nvl takes exactly 2
   arguments, no more), so maybe there is nothing 'official' you can do,
   but can you help me work it out for my project?

   I assume it is very similar to what you helped me out with
   above...something like this:

   
   from sqlalchemy.sql.expression import ColumnElement
   from sqlalchemy.ext.compiler import compiles
   from sqlalchemy.types import DateTime, Date

   class current_date(ColumnElement):
       type = Date()

   @compiles(current_date)
   def _compiler_dispatch(element, compiler, **kw):
       if compiler.dialect.name == 'oracle':
           if compiler.dialect.use_ansi:
               return trunc(current_date)
           else:
               return trunc(sysdate)
       else:
           # assume postgres
           return current_date
   

   But the main difference is it takes arguments.

   Is there a clever way to return the appropriate function, something
   like this:

   def 
       if compiler.dialect.name == 'oracle':
           return func.nvl
       else:
           # assume postgres
           return func.coalesce

  I will add this to the docs:

  from sqlalchemy import *
  from sqlalchemy.ext.compiler import compiles

  from sqlalchemy.sql.expression import FunctionElement

  class coalesce(FunctionElement):
     name = 'coalesce'

  @compiles(coalesce)
  def compile(element, compiler, **kw):
     return coalesce(%s) % compiler.process(element.clauses)

  @compiles(coalesce, 'oracle')
  def compile(element, compiler, **kw):
     if len(element.clauses)  2:
         raise TypeError(coalesce only supports two arguments on Oracle)
     return nvl(%s) % compiler.process(element.clauses)

  print coalesce(5, 6)

  from sqlalchemy.dialects import oracle
  print coalesce(5, 6).compile(dialect=oracle.dialect())

 Might this work as a more complete solution for Oracle?

 @compiles(coalesce, 'oracle')
 def compile(element, compiler, **kw):
    sql = nvl(%s)
    for i in xrange(len(element.clauses) - 2):
       sql %= %s, nvl(%%s) % compiler.process(element.clauses[i:i+1])
    return sql % compiler.process(element.clauses[-2:])

 Ian

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Re: [sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Kent Bower]

By the way,
Unless a ClauseList is subscriptable in 0.6, I had problems the way 
it was.


Here is what I did:

@compiles(coalesce, 'oracle')
def compile(element, compiler, **kw):
sql = nvl(%s)
clauses = map(compiler.process, element.clauses)
for i in xrange(len(clauses) - 2):
sql %= %s, nvl(%%s) % clauses[i]
return sql % , .join(clauses[-2:])



On 4/2/2010 7:08 PM, Ian Kelly wrote:
On Fri, Apr 2, 2010 at 3:41 PM, Michael Bayer 
mike...@zzzcomputing.com mailto:mike...@zzzcomputing.com wrote:


Kent wrote:
 Along the same lines, is there something we can do about nvl()
 (oracle) versus coalesce() (ansi)?

 They aren't exactly the same, unfortunately (nvl takes exactly 2
 arguments, no more), so maybe there is nothing 'official' you
can do,
 but can you help me work it out for my project?

 I assume it is very similar to what you helped me out with
 above...something like this:

 
 from sqlalchemy.sql.expression import ColumnElement
 from sqlalchemy.ext.compiler import compiles
 from sqlalchemy.types import DateTime, Date

 class current_date(ColumnElement):
 type = Date()

 @compiles(current_date)
 def _compiler_dispatch(element, compiler, **kw):
 if compiler.dialect.name http://compiler.dialect.name ==
'oracle':
 if compiler.dialect.use_ansi:
 return trunc(current_date)
 else:
 return trunc(sysdate)
 else:
 # assume postgres
 return current_date
 


 But the main difference is it takes arguments.

 Is there a clever way to return the appropriate function, something
 like this:

 def 
 if compiler.dialect.name http://compiler.dialect.name ==
'oracle':
 return func.nvl
 else:
 # assume postgres
 return func.coalesce

I will add this to the docs:


from sqlalchemy import *
from sqlalchemy.ext.compiler import compiles

from sqlalchemy.sql.expression import FunctionElement


class coalesce(FunctionElement):
   name = 'coalesce'

@compiles(coalesce)
def compile(element, compiler, **kw):
   return coalesce(%s) % compiler.process(element.clauses)


@compiles(coalesce, 'oracle')
def compile(element, compiler, **kw):
   if len(element.clauses)  2:
   raise TypeError(coalesce only supports two arguments on
Oracle)
   return nvl(%s) % compiler.process(element.clauses)

print coalesce(5, 6)

from sqlalchemy.dialects import oracle
print coalesce(5, 6).compile(dialect=oracle.dialect())


Might this work as a more complete solution for Oracle?

@compiles(coalesce, 'oracle')
def compile(element, compiler, **kw):
   sql = nvl(%s)
   for i in xrange(len(element.clauses) - 2):
  sql %= %s, nvl(%%s) % compiler.process(element.clauses[i:i+1])
   return sql % compiler.process(element.clauses[-2:])

Ian
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[sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Kent]

Any chance you plan to make func.now consider oracle and
use_ansi=False (and return sysdate)?



On Feb 3, 4:44 pm, Michael Bayer mike...@zzzcomputing.com wrote:
 Kent wrote:
  Any chance SQLAlchemy has a mechanism to switch to or fromsysdatevs.
 current_datebased on the database dialect (and maybe use_ansi)?

  It would be really nice if I could program in sqla not knowing which
  database type I am connected to and still could select the current
  date from the database... can I?

 func.now() does do this (well, it returns CURRENT_TIMESTAMP, 
 isCURRENT_DATEdifferent?).   it doesn't take use_ansi into account though
 (though that would be an easy patch to theOracledialect).

 Aside from all that, this is also easy enough to roll yourself:

 from sqlalchemy.sql.expression import ColumnElement
 from sqlalchemy.ext.compiler import compiles

 classcurrent_date(ColumnElement):
     type = sa.DateTime()

 @compiler.compiles(current_date)
 def _compiler_dispatch(element, compiler, **kw):
     if compiler.dialect.name == 'oracle':
         if not compiler.dialect.use_ansi:
             return sysdate
         else:
             return current_date
     else:
         # etc ...

 then just saycurrent_date() to get the expression.

 you could also throw @compiles onto sqlalchemy.sql.functions.now if you
 wanted to augment what func.now() returns.



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Re: [sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Michael Bayer]

Kent wrote:
 Any chance you plan to make func.now consider oracle and
 use_ansi=False (and return sysdate)?

the use_ansi flag should be removed as far as public API since we can
detect server version now.   we can also make now() return sysdate()
unconditionally on oracle, you should give us a trac ticket for the latter
on milestone 0.6.






 On Feb 3, 4:44 pm, Michael Bayer mike...@zzzcomputing.com wrote:
 Kent wrote:
  Any chance SQLAlchemy has a mechanism to switch to or fromsysdatevs.
 current_datebased on the database dialect (and maybe use_ansi)?

  It would be really nice if I could program in sqla not knowing which
  database type I am connected to and still could select the current
  date from the database... can I?

 func.now() does do this (well, it returns CURRENT_TIMESTAMP,
 isCURRENT_DATEdifferent?).   it doesn't take use_ansi into account
 though
 (though that would be an easy patch to theOracledialect).

 Aside from all that, this is also easy enough to roll yourself:

 from sqlalchemy.sql.expression import ColumnElement
 from sqlalchemy.ext.compiler import compiles

 classcurrent_date(ColumnElement):
     type = sa.DateTime()

 @compiler.compiles(current_date)
 def _compiler_dispatch(element, compiler, **kw):
     if compiler.dialect.name == 'oracle':
         if not compiler.dialect.use_ansi:
             return sysdate
         else:
             return current_date
     else:
         # etc ...

 then just saycurrent_date() to get the expression.

 you could also throw @compiles onto sqlalchemy.sql.functions.now if
 you
 wanted to augment what func.now() returns.



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[sqlalchemy] Re: use_ansi oracle sysdate vs. current_date

[Kent]

Many thanks.


On Feb 3, 3:44 pm, Michael Bayer mike...@zzzcomputing.com wrote:
 Kent wrote:
  Any chance SQLAlchemy has a mechanism to switch to or from sysdate vs.
  current_date based on the database dialect (and maybe use_ansi)?

  It would be really nice if I could program in sqla not knowing which
  database type I am connected to and still could select the current
  date from the database... can I?

 func.now() does do this (well, it returns CURRENT_TIMESTAMP, is
 CURRENT_DATE different?).   it doesn't take use_ansi into account though
 (though that would be an easy patch to the Oracle dialect).

 Aside from all that, this is also easy enough to roll yourself:

 from sqlalchemy.sql.expression import ColumnElement
 from sqlalchemy.ext.compiler import compiles

 class current_date(ColumnElement):
     type = sa.DateTime()

 @compiler.compiles(current_date)
 def _compiler_dispatch(element, compiler, **kw):
     if compiler.dialect.name == 'oracle':
         if not compiler.dialect.use_ansi:
             return sysdate
         else:
             return current_date
     else:
         # etc ...

 then just say current_date() to get the expression.

 you could also throw @compiles onto sqlalchemy.sql.functions.now if you
 wanted to augment what func.now() returns.





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