cache

src/caosadvancedtools/cfood.py

@@ -26,8 +26,10 @@
 
 import argparse
 import re
+from hashlib import sha256
 from argparse import RawTextHelpFormatter
 from datetime import datetime
+import sqlite3 
 
 import caosdb as db
 from caosdb.exceptions import TransactionError
@@ -38,16 +40,77 @@ def get_entity(name):
     ent.retrieve()
 
     return ent
+                                                                                
+def get_pretty_xml(cont):                                                       
+    if isinstance(cont, list):                                                  
+        cont = db.Container().extend(cont)                                      
+    if isinstance(cont, db.Entity):                                                  
+        cont = db.Container().insert(cont)                                      
+                                                                                
+    return etree.tounicode(cont.to_xml(                                         
+        local_serialization=True), pretty_print=True)                           
+
+
+# TODO this is implementing a cache on client side. Should it be on
+# server side?
+class Cache(object):
+    CACHE_DB = "cache.db"
+    def __init__(self):
+        if not os.path.exists(Cache.CACHE_DB):
+            self.create_cache()
+
+    def create_cache(self):
+        conn = sqlite3.connect(Cache.CACHE_DB)
+        c = conn.cursor()
+        c.execute('''CREATE TABLE identifiables (digest text primary key, caosdb_id integer)''')
+        conn.commit()
+        conn.close()
+
+    def hash_entity(ent):
+        xml = get_pretty_xml(ent)
+        digest = sha256(xml.encode("utf-8")).hexdigest()
+
+    def insert(ent):
+        conn = sqlite3.connect(Cache.CACHE_DB)
+        c = conn.cursor()
+        c.execute('''INSERT INTO identifiables VALUES ({}, {})'''.format(
+            Cache.hash_entity(ent), ent.id)
+        )
+        conn.commit()
+        conn.close()
+
+    def check_existing(ent):
+        conn = sqlite3.connect(Cache.CACHE_DB)
+        c = conn.cursor()
+        c.execute('''Select  * FROM stocks WHERE digest=?''', Cache.hash_entity(ent))
+        res =  c.fetchone()
+        conn.commit()
+        conn.close()
+        return res
+
 
 
 class AbstractCFood(object):
-    def __init__(self, pattern):
+    # TODO restructure this class such that no instance is needed to check for
+    # a match
+    # instances shall be used to keep track of a match; i.e. entities can be
+    # object variable
+    def __init__(self, pattern, use_cache=False):
         self.pattern = re.compile(pattern)
+        self.use_cache = use_cache
 
     def treat_match(self, crawled_file, match):
         entities = self.create_identifiables(crawled_file, match)
 
         for key, ent in entities.items():
+            existing = None
+            if self.use_cache:
+                c = Cache()
+                existing_in_cache = c.check_existing(ent)
+                if existing_in_cache is not None:
+                    existing = db.Entity(id = existing_in_cache).retrieve()
+
+
             existing = AbstractCFood.find_existing(ent)
 
             if existing is None: