|
| 1 | +from django.db import models |
| 2 | +from django.db.models import Func, Value, F |
| 3 | +from django.db.models.functions import Cast |
| 4 | +import pgvector.django |
| 5 | +import json |
| 6 | + |
| 7 | + |
| 8 | +class GenerateEmbedding(Func): |
| 9 | + function = "pgml.embed" |
| 10 | + template = "%(function)s('%(transformer)s', %(expressions)s, '%(parameters)s')" |
| 11 | + allowed_default = False |
| 12 | + |
| 13 | + def __init__(self, expression, transformer, parameters={}): |
| 14 | + self.transformer = transformer |
| 15 | + self.parameters = parameters |
| 16 | + super().__init__(expression) |
| 17 | + |
| 18 | + def as_sql(self, compiler, connection, **extra_context): |
| 19 | + extra_context["transformer"] = self.transformer |
| 20 | + extra_context["parameters"] = json.dumps(self.parameters) |
| 21 | + return super().as_sql(compiler, connection, **extra_context) |
| 22 | + |
| 23 | + |
| 24 | +class Embed(models.Model): |
| 25 | + class Meta: |
| 26 | + abstract = True |
| 27 | + |
| 28 | + def save(self, *args, **kwargs): |
| 29 | + update_fields = kwargs.get("update_fields") |
| 30 | + |
| 31 | + # Check for fields to embed |
| 32 | + for field in self._meta.get_fields(): |
| 33 | + if isinstance(field, VectorField): |
| 34 | + if not hasattr(self, field.field_to_embed): |
| 35 | + raise AttributeError( |
| 36 | + f"Field to embed does not exist: `{field.field_to_embed}`" |
| 37 | + ) |
| 38 | + |
| 39 | + # Only embed if it's a new instance, full save, or this field is being updated |
| 40 | + if not self.pk or update_fields is None or field.name in update_fields: |
| 41 | + value_to_embed = getattr(self, field.field_to_embed) |
| 42 | + setattr( |
| 43 | + self, |
| 44 | + field.name, |
| 45 | + GenerateEmbedding( |
| 46 | + Value(value_to_embed), |
| 47 | + field.transformer, |
| 48 | + field.transformer_store_parameters, |
| 49 | + ), |
| 50 | + ) |
| 51 | + |
| 52 | + super().save(*args, **kwargs) |
| 53 | + |
| 54 | + @classmethod |
| 55 | + def vector_search( |
| 56 | + cls, field, query_text, distance_function=pgvector.django.CosineDistance |
| 57 | + ): |
| 58 | + # Get the fields |
| 59 | + field_instance = getattr(cls._meta.model, field).field |
| 60 | + |
| 61 | + # Generate an embedding for the text |
| 62 | + query_embedding = GenerateEmbedding( |
| 63 | + Value(query_text), |
| 64 | + "intfloat/e5-small-v2", |
| 65 | + field_instance.transformer_recall_parameters, |
| 66 | + ) |
| 67 | + |
| 68 | + # Return the QuerySet |
| 69 | + return cls.objects.annotate( |
| 70 | + distance=distance_function( |
| 71 | + F(field), |
| 72 | + Cast( |
| 73 | + query_embedding, |
| 74 | + output_field=VectorField(dimensions=field_instance.dimensions), |
| 75 | + ), |
| 76 | + ) |
| 77 | + ).order_by("distance") |
| 78 | + |
| 79 | + |
| 80 | +class VectorField(pgvector.django.VectorField): |
| 81 | + def __init__( |
| 82 | + self, |
| 83 | + field_to_embed=None, |
| 84 | + dimensions=None, |
| 85 | + transformer=None, |
| 86 | + transformer_store_parameters={}, |
| 87 | + transformer_recall_parameters={}, |
| 88 | + *args, |
| 89 | + **kwargs, |
| 90 | + ): |
| 91 | + self.field_to_embed = field_to_embed |
| 92 | + self.transformer = transformer |
| 93 | + self.transformer_store_parameters = transformer_store_parameters |
| 94 | + self.transformer_recall_parameters = transformer_recall_parameters |
| 95 | + super().__init__(dimensions=dimensions, *args, **kwargs) |
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