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Diffstat (limited to 'examples/berkeleydb_example.py')
| -rw-r--r-- | examples/berkeleydb_example.py | 134 |
1 files changed, 134 insertions, 0 deletions
diff --git a/examples/berkeleydb_example.py b/examples/berkeleydb_example.py new file mode 100644 index 00000000..d50352b1 --- /dev/null +++ b/examples/berkeleydb_example.py @@ -0,0 +1,134 @@ +""" +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 +from rdflib.store import NO_STORE, VALID_STORE +from tempfile import mktemp + + +def example_1(): + """Creates a ConjunctiveGraph and performs some BerkeleyDB tasks with it + """ + path = mktemp() + + # 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 = graph.open(path, create=False) + + if rt == NO_STORE: + # There is no underlying BerkeleyDB infrastructure, so create it + print("Creating new DB") + graph.open(path, 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("http://example.net/test/") + graph.bind("eg", EG) + + graph.add((EG["pic:1"], EG.name, Literal("Jane & Bob"))) + graph.add((EG["pic:2"], EG.name, 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") + + graph.open(path, 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) + + +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") + g.open("gsg_vocabs", create=True) + + # gsq_vocabs = "https://api.github.com/repos/geological-survey-of-queensland/vocabularies/git/trees/master" + gsq_vocabs = "https://api.github.com/repos/geological-survey-of-queensland/vocabularies/git/trees/cd7244d39337c1f4ef164b1cf1ea1f540a7277db" + try: + res = urlopen(Request(gsq_vocabs, headers={"Accept": "application/json"})) + except HTTPError as e: + return e.code, str(e), None + + data = res.read() + encoding = res.info().get_content_charset('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(r.read().decode())["content"] + g.parse(data=base64.b64decode(content).decode(), format="turtle") + print(len(g)) + + print("loading complete") + + +if __name__ == "__main__": + example_1() + example_2() |
