Iain Duncan <iainduncanli...@gmail.com> writes:
> Hi folks, I've been googling and cargo culting to no avail here, hope
> someone can help.
> I'm trying to get an app running on MySQL on OS X, that was running fine on
> MySQL on Linux.
>
> The issue is I have some large composite primarky keys:
>
> class VarTrigger(Base):
> "assoc table that associates actions when a var is set"
> __tablename__ = "var_trigger"
> # actual primary key is var_id, p_value
> var_id = Column(Integer, ForeignKey("var.id"), nullable=True,
> primary_key=True)
> p_value = Column( String(255), primary_key=True, nullable=False )
> ...
>
> When I try to create the tables I'm getting the following:
>
> qlalchemy.exc.OperationalError: (OperationalError) (1709, 'Index column
> size too large. The maximum column size is 767 bytes.')
>
Most probably, the MySQL settings differ from one installation to the
other, and on OS X the database has been created with UTF-8 as default
codec. At that point, MySQL considers that each "character" in a string
*may* consume up to 3 (or 4, depending on the exact codec) bytes, so it
assume that your "p_value" string needs 255*3 bytes, that summed with
"var_id" size exceeds maximum allowed index entry size.
There may be some setting to change that limit.
> I've been trying out things like changing character collation and so one
> with no luck.
Collation is different from the encoding: the former defines the
ordering rules, the latter the actual content encoding (that is, how the
data is written to permanent storage).
hth, ciao, lele.
--
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
l...@metapensiero.it | -- Fortunato Depero, 1929.
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