Source code for examples.berkeleydb_example

BerkeleyDB in use as a persistent Graph store.

Example 1: simple actions

* creating a ConjunctiveGraph using the BerkeleyDB Store
* adding triples to it
* counting them
* closing the store, emptying the graph
* re-opening the store using the same DB files
* getting the same count of triples as before

Example 2: larger data

* loads multiple graphs downloaded from GitHub into a BerkeleyDB-baked graph stored in the folder gsq_vocabs.
* does not delete the DB at the end so you can see it on disk
import os
from rdflib import ConjunctiveGraph, Namespace, Literal
import tempfile

[docs]def example_1(): """Creates a ConjunctiveGraph and performs some BerkeleyDB tasks with it""" path = tempfile.NamedTemporaryFile().name # Declare we are using a BerkeleyDB Store graph = ConjunctiveGraph("BerkeleyDB") # Open previously created store, or create it if it doesn't exist yet # (always doesn't exist in this example as using temp file location) rt =, create=False) if rt == NO_STORE: # There is no underlying BerkeleyDB infrastructure, so create it print("Creating new DB"), create=True) else: print("Using existing DB") assert rt == VALID_STORE, "The underlying store is corrupt" print("Triples in graph before add:", len(graph)) print("(will always be 0 when using temp file for DB)") # Now we'll add some triples to the graph & commit the changes EG = Namespace("") graph.bind("eg", EG) graph.add((EG["pic:1"],, Literal("Jane & Bob"))) graph.add((EG["pic:2"],, Literal("Squirrel in Tree"))) graph.commit() print("Triples in graph after add:", len(graph)) print("(should be 2)") # display the graph in Turtle print(graph.serialize()) # close when done, otherwise BerkeleyDB will leak lock entries. graph.close() graph = None # reopen the graph graph = ConjunctiveGraph("BerkeleyDB"), create=False) print("Triples still in graph:", len(graph)) print("(should still be 2)") graph.close() # Clean up the temp folder to remove the BerkeleyDB database files... for f in os.listdir(path): os.unlink(path + "/" + f) os.rmdir(path)
[docs]def example_2(): """Loads a number of SKOS vocabularies from GitHub into a BerkeleyDB-backed graph stored in the local folder 'gsq_vocabs' Should print out the number of triples after each load, e.g.: 177 248 289 379 421 628 764 813 965 1381 9666 9719 ... """ from urllib.request import urlopen, Request from urllib.error import HTTPError import json import base64 g = ConjunctiveGraph("BerkeleyDB")"gsg_vocabs", create=True) # gsq_vocabs = "" gsq_vocabs = "" try: res = urlopen(Request(gsq_vocabs, headers={"Accept": "application/json"})) except HTTPError as e: return e.code, str(e), None data = encoding ="utf-8") j = json.loads(data.decode(encoding)) for v in j["tree"]: # process the element in GitHub result if it's a Turtle file if v["path"].endswith(".ttl"): # for each file, call it by URL, decode it and parse it into the graph r = urlopen(v["url"]) content = json.loads(["content"] g.parse(data=base64.b64decode(content).decode(), format="turtle") print(len(g)) print("loading complete")
if __name__ == "__main__": example_1() example_2()