peewee multiplying integer fields by floats for linear expression – replaces numbers between 0 and 1 with 0
Question:
I am trying to add a linear inequality to a select statement in peewee,
r = r.where((tgt.attrs.NumberMissingOriginalIntrons <= 0.5 * tgt.attrs.NumberIntrons - 0.5))
Where r is an existing query being added to and tgt.attrs is a table.
However, when this is converted to SQL, it looks like this:
WHERE ("t1"."NumberMissingOriginalIntrons" <= ((? * "t1"."NumberIntrons") - ?)) [0, 0]
But the expression I actually want is:
WHERE ("t1"."NumberMissingOriginalIntrons" <= ((? * "t1"."NumberIntrons") - ?)) [0.5, 0.5]
Based on some testing, I have realized that this only fails if the values are between 0 and 1. Why is this? Does this have to do with the column definitions being Integer?
Answers:
Yes, it’s related with your column field type (Integer).
Nevertheless, you can use the cast function:
from playhouse.shortcuts import cast
...
my_field = tgt.attrs.NumberMissingOriginalIntrons
r = r.where((cast(my_field, 'float') <= 0.5 * cast(my_field, 'float') - 0.5))
In recent versions(Currently, up to v3.15), this function is inside peewee itself and there is no need to import playhous.shortcuts .
Also, the function name been changed from cast to Cast a few years after el.atomo answered the question. (as mentioned in the Cast documentation)
So for the code example above, we will have:
my_field = tgt.attrs.NumberMissingOriginalIntrons
r = r.where((cast(my_field, 'float') <= 0.5 * Cast(my_field, 'float') - 0.5))
I am trying to add a linear inequality to a select statement in peewee,
r = r.where((tgt.attrs.NumberMissingOriginalIntrons <= 0.5 * tgt.attrs.NumberIntrons - 0.5))
Where r is an existing query being added to and tgt.attrs is a table.
However, when this is converted to SQL, it looks like this:
WHERE ("t1"."NumberMissingOriginalIntrons" <= ((? * "t1"."NumberIntrons") - ?)) [0, 0]
But the expression I actually want is:
WHERE ("t1"."NumberMissingOriginalIntrons" <= ((? * "t1"."NumberIntrons") - ?)) [0.5, 0.5]
Based on some testing, I have realized that this only fails if the values are between 0 and 1. Why is this? Does this have to do with the column definitions being Integer?
Yes, it’s related with your column field type (Integer).
Nevertheless, you can use the cast function:
from playhouse.shortcuts import cast
...
my_field = tgt.attrs.NumberMissingOriginalIntrons
r = r.where((cast(my_field, 'float') <= 0.5 * cast(my_field, 'float') - 0.5))
In recent versions(Currently, up to v3.15), this function is inside peewee itself and there is no need to import playhous.shortcuts .
Also, the function name been changed from cast to Cast a few years after el.atomo answered the question. (as mentioned in the Cast documentation)
So for the code example above, we will have:
my_field = tgt.attrs.NumberMissingOriginalIntrons
r = r.where((cast(my_field, 'float') <= 0.5 * Cast(my_field, 'float') - 0.5))