Feature/schema from existing graph

examples/customize/build_graph/components/schema_builders/schema_from_existing_graph.py

@@ -0,0 +1,35 @@
+"""This example demonstrates how to use the SchemaFromExistingGraphExtractor component
+to automatically extract a schema from an existing Neo4j database.
+"""
+
+import asyncio
+
+import neo4j
+
+from neo4j_graphrag.experimental.components.schema import (
+    SchemaFromExistingGraphExtractor,
+    GraphSchema,
+)
+
+
+URI = "neo4j+s://demo.neo4jlabs.com"
+AUTH = ("recommendations", "recommendations")
+DATABASE = "recommendations"
+INDEX = "moviePlotsEmbedding"
+
+
+async def main() -> None:
+    """Run the example."""
+
+    with neo4j.GraphDatabase.driver(
+        URI,
+        auth=AUTH,
+    ) as driver:
+        extractor = SchemaFromExistingGraphExtractor(driver)
+        schema: GraphSchema = await extractor.run()
+        # schema.store_as_json("my_schema.json")
+        print(schema)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

src/neo4j_graphrag/experimental/components/schema.py

@@ -15,6 +15,8 @@
 from __future__ import annotations
 
 import json
+
+import neo4j
 import logging
 import warnings
 from typing import Any, Dict, List, Literal, Optional, Tuple, Union, Sequence
@@ -43,6 +45,7 @@
 from neo4j_graphrag.generation import SchemaExtractionTemplate, PromptTemplate
 from neo4j_graphrag.llm import LLMInterface
 from neo4j_graphrag.utils.file_handler import FileHandler, FileFormat
+from neo4j_graphrag.schema import get_structured_schema
 
 
 class PropertyType(BaseModel):
@@ -270,7 +273,12 @@ def from_file(
             raise SchemaValidationError(str(e)) from e
 
 
-class SchemaBuilder(Component):
+class BaseSchemaBuilder(Component):
+    async def run(self, *args: Any, **kwargs: Any) -> GraphSchema:
+        raise NotImplementedError()
+
+
+class SchemaBuilder(BaseSchemaBuilder):
     """
     A builder class for constructing GraphSchema objects from given entities,
     relations, and their interrelationships defined in a potential schema.
@@ -379,7 +387,7 @@ async def run(
         return self.create_schema_model(node_types, relationship_types, patterns)
 
 
-class SchemaFromTextExtractor(Component):
+class SchemaFromTextExtractor(BaseSchemaBuilder):
     """
     A component for constructing GraphSchema objects from the output of an LLM after
     automatic schema extraction from text.
@@ -462,3 +470,146 @@ async def run(self, text: str, examples: str = "", **kwargs: Any) -> GraphSchema
                 "patterns": extracted_patterns,
             }
         )
+
+
+class SchemaFromExistingGraphExtractor(BaseSchemaBuilder):
+    """A class to build a GraphSchema object from an existing graph.
+
+    Uses the get_structured_schema function to extract existing node labels,
+    relationship types, properties and existence constraints.
+
+    By default, the built schema does not allow any additional item (property,
+    node label, relationship type or pattern).
+
+       Args:
+            driver (neo4j.Driver): connection to the neo4j database.
+            additional_properties (bool, default False): see GraphSchema
+            additional_node_types (bool, default False): see GraphSchema
+            additional_relationship_types (bool, default False): see GraphSchema:
+            additional_patterns (bool, default False): see GraphSchema:
+            neo4j_database (Optional | str): name of the neo4j database to use
+    """
+
+    def __init__(
+        self,
+        driver: neo4j.Driver,
+        additional_properties: bool = False,
+        additional_node_types: bool = False,
+        additional_relationship_types: bool = False,
+        additional_patterns: bool = False,
+        neo4j_database: Optional[str] = None,
+    ) -> None:
+        self.driver = driver
+        self.database = neo4j_database
+
+        self.additional_properties = additional_properties
+        self.additional_node_types = additional_node_types
+        self.additional_relationship_types = additional_relationship_types
+        self.additional_patterns = additional_patterns
+
+    @staticmethod
+    def _extract_required_properties(
+        structured_schema: dict[str, Any],
+    ) -> list[tuple[str, str]]:
+        """Extract a list of (node label (or rel type), property name) for which
+         an "EXISTENCE" or "KEY" constraint is defined in the DB.
+
+         Args:
+
+             structured_schema (dict[str, Any]): the result of the `get_structured_schema()` function.
+
+        Returns:
+
+            list of tuples of (node label (or rel type), property name)
+
+        """
+        schema_metadata = structured_schema.get("metadata", {})
+        existence_constraint = []  # list of (node label, property name)
+        for constraint in schema_metadata.get("constraints", []):
+            if constraint["type"] in (
+                "NODE_PROPERTY_EXISTENCE",
+                "NODE_KEY",
+                "RELATIONSHIP_PROPERTY_EXISTENCE",
+                "RELATIONSHIP_KEY",
+            ):
+                properties = constraint["properties"]
+                labels = constraint["labelsOrTypes"]
+                # note: existence constraint only apply to a single property
+                # and a single label
+                prop = properties[0]
+                lab = labels[0]
+                existence_constraint.append((lab, prop))
+        return existence_constraint
+
+    async def run(self) -> GraphSchema:
+        structured_schema = get_structured_schema(self.driver, database=self.database)
+        existence_constraint = self._extract_required_properties(structured_schema)
+
+        node_labels = set(structured_schema["node_props"].keys())
+        node_types = [
+            {
+                "label": key,
+                "properties": [
+                    {
+                        "name": p["property"],
+                        "type": p["type"],
+                        "required": (key, p["property"]) in existence_constraint,
+                    }
+                    for p in properties
+                ],
+                "additional_properties": self.additional_properties,
+            }
+            for key, properties in structured_schema["node_props"].items()
+        ]
+        rel_labels = set(structured_schema["rel_props"].keys())
+        relationship_types = [
+            {
+                "label": key,
+                "properties": [
+                    {
+                        "name": p["property"],
+                        "type": p["type"],
+                        "required": (key, p["property"]) in existence_constraint,
+                    }
+                    for p in properties
+                ],
+            }
+            for key, properties in structured_schema["rel_props"].items()
+        ]
+        patterns = [
+            (s["start"], s["type"], s["end"])
+            for s in structured_schema["relationships"]
+        ]
+        # deal with nodes and relationships without properties
+        for source, rel, target in patterns:
+            if source not in node_labels:
+                node_labels.add(source)
+                node_types.append(
+                    {
+                        "label": source,
+                    }
+                )
+            if target not in node_labels:
+                node_labels.add(target)
+                node_types.append(
+                    {
+                        "label": target,
+                    }
+                )
+            if rel not in rel_labels:
+                rel_labels.add(rel)
+                relationship_types.append(
+                    {
+                        "label": rel,
+                    }
+                )
+        return GraphSchema.model_validate(
+            {
+                "node_types": node_types,
+                "relationship_types": relationship_types,
+                "patterns": patterns,
+                "additional_node_types": self.additional_node_types,
+                "additional_relationship_types": self.additional_relationship_types,
+                "additional_patterns": self.additional_patterns,
+            }
+        )