db: Implement SQL statement rewriting

We now have an abstract rewriter that will perform some common extractions and
replacements (type replacement for example), that can then be customized in
derived classes.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

.gitignore

@@ -8,6 +8,7 @@
 *.gcno
 *.dSYM
 *.rej
+*.po
 *.pyc
 .cppcheck-suppress
 TAGS

devtools/sql-rewrite.py

@@ -2,16 +2,69 @@
 
 from mako.template import Template
 
+import re
 import sys
 
 
-class Sqlite3Rewriter(object):
-    def rewrite(self, query):
+DEBUG = False
+
+
+def eprint(*args, **kwargs):
+    if not DEBUG:
+        return
+    print(*args, **kwargs, file=sys.stderr)
+
+
+class Rewriter(object):
+
+    def rewrite_types(self, query, mapping):
+        for old, new in mapping.items():
+            query = re.sub(old, new, query)
         return query
 
+    def rewrite_single(self, query):
+        return query
+
+    def rewrite(self, queries):
+        for i, q in enumerate(queries):
+            org = q['query']
+            queries[i]['query'] = self.rewrite_single(org)
+            eprint("Rewritten statement\n\tfrom {}\n\t  to {}".format(org, q['query']))
+        return queries
+
+
+class Sqlite3Rewriter(Rewriter):
+    def rewrite_single(self, query):
+        typemapping = {
+            r'BIGINT': 'INTEGER',
+            r'BIGINTEGER': 'INTEGER',
+            r'BIGSERIAL': 'INTEGER',
+            r'CURRENT_TIMESTAMP\(\)': "strftime('%s', 'now')",
+            r'INSERT INTO[ \t]+(.*)[ \t]+ON CONFLICT.*DO NOTHING;': 'INSERT OR IGNORE INTO \\1;',
+        }
+        return self.rewrite_types(query, typemapping)
+
+
+class PostgresRewriter(Rewriter):
+    def rewrite_single(self, q):
+        # Let's start by replacing any eventual '?' placeholders
+        q2 = ""
+        count = 1
+        for c in q:
+            if c == '?':
+                c = "${}".format(count)
+                count += 1
+            q2 += c
+        query = q2
+
+        typemapping = {
+            r'BLOB': 'BYTEA',
+            r'CURRENT_TIMESTAMP\(\)': "EXTRACT(epoch FROM now())",
+        }
+
+        query = self.rewrite_types(query, typemapping)
+        return query
 
-class PostgresRewriter(Sqlite3Rewriter):
-    pass
 
 rewriters = {
     "sqlite3": Sqlite3Rewriter(),
@@ -66,7 +119,6 @@ def extract_queries(pofile):
 
     queries = []
     for c in chunk(pofile):
-        name = c[0][3:]
 
         # Skip other comments
         i = 1