set next value of postgres sequence

[Chris Withers]

Hi All,

What's the recommended way to set the next value of a postgres sequence
when using sqlalchemy?

cheers,

Chris

[Jonathan Vanasco]

There is a `Sequence` object that can be delcared like a table

From the docs:

http://docs.sqlalchemy.org/en/latest/core/defaults.html#defining-sequences

seq = Sequence('some_sequence')
nextid = connection.execute(seq)

[Chris Withers]

Indeed, but that's not quite what I asked ;-)

I'm after setting the next value using, eg, setval:

http://www.postgresql.org/docs/current/static/functions-sequence.html

...or to do it on creation of the sequence:

http://www.postgresql.org/docs/current/static/sql-createsequence.html

I guess this might come into the stuff I was asking about in the "non-table DDL elements and MetaData objects" thread.

Chris

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[Jonathan Vanasco]

On Tuesday, December 1, 2015 at 3:39:02 PM UTC-5, Chris Withers wrote:

Indeed, but that's not quite what I asked ;-)

I'm after setting the next value using, eg, setval:

Ah, sorry.  I saw "next value" and thought "nextval", not setval.  

The `Sequence` object just seems to support a 'next_value()' http://docs.sqlalchemy.org/en/latest/core/defaults.html#sqlalchemy.schema.Sequence

I looked in the source, and it looks like the postgres dialect only has a `nextval` operation.  Sqlalchemy's compiler and dialects seem to only support `create sequence` and `nextval` (there's no "alter sequence [restart with]" or "setval" equivalents).   It looks like you can only pass in a start value for the sequence on creation.

I think you may need to handle this with literal sql, and create a ticket or try to patch.