django-sequencefield 1.0.0

Additional field from django taking it's value from a postgresql sequence. It is similar to django AutoField, except that multiple model can share ids from a single sequence. Also add the possibility to generate an id from a sequence AND from the data of another field in the model

sequencefield

simple model field taking it's value from a postgres sequence. This is an easy replacement for django autofield offering the following advantages:

• Sequence could be shared among multiple models (db tables), so you can now have unique id among multiple django models
• Unique Id could also be combined with data from other field to build complex id. One example is given that combine unique id with date information to offer an efficient table indexing/clustering for faster data retrieval when filtering on date. (Particularly useful with BRIN index)

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Installation

• Run pip install sequencefield
• Use a (Small/Big)IntegerSequenceField in one of your model
• Add a SequenceConstraint into the same model to name the sequence field to use and which id should take values from this sequence constraint

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Usage

Settings

This package doesn't need any setting.

Simple Example

Just add a sequence field(s) to your models like this:

from django.db import models
from sequencefield.constraints import IntSequenceConstraint
from sequencefield.fields import IntegerSequenceField


class IntSequenceModel(models.Model):
    id = IntegerSequenceField(primary_key=True) #primary_key=False works too

    class Meta:
        constraints = [
            IntSequenceConstraint(
                name="%(app_label)s_%(class)s_custseq",
                sequence="int_custseq", #name of sequence to use
                fields=["id"], #name of the field that should be populated by this sequence
                start=100, #first value of the sequence
                maxvalue=200 #max value allowed for the sequence, will raise error if we go above, use None for the maximum allowed value of the db
            )
        ]

Advance Example

Just add a sequence field(s) to your models like this:

from django.db import models
from sequencefield.constraints import BigIntSequenceConstraint
from sequencefield.fields import BigIntegerWithDateSequenceField


class BigIntSequenceModel(models.Model):
    id = models.BigIntegerField(primary_key=True, auto_created=False)
    created = models.DateTimeField(editable=False)
    seqid = BigIntegerWithDateSequenceField(datetime_field="created") #this field with combine values from the sequence with date timestamp
    # the 2 first bytes of the bigint will contains the number of days since 1/1/1970
    # the 6 following bytes will contains a unique id coming from the sequence

    class Meta:
        constraints = [
            BigIntSequenceConstraint(
                name="%(app_label)s_%(class)s_custseq",
                sequence="gdw_post_custseq", #name of the quence
                fields=["seqid"], #field to be populated from this sequence
                start=1, #first value of the sequence
            )
        ]

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Testing

# clone repository
git clone https://github.com/quertenmont/sequencefield.git && cd sequencefield

# create virtualenv and activate it
python -m venv venv && . venv/bin/activate

# upgrade pip
python -m pip install --upgrade pip

# install requirements
pip install -r requirements.txt -r requirements-test.txt

# install pre-commit to run formatters and linters
pre-commit install --install-hooks

# run tests
tox
# or
python runtests.py
# or
python -m django test --settings "tests.settings"

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License

Released under MIT License.

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Supporting

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