Compute SHA256 for each table and store it if has changed

audit/changed_tables

@@ -0,0 +1,83 @@
+#!/usr/bin/python3
+
+import argparse
+import datetime
+import logging
+import os
+import psycopg2
+from   psycopg2.extras import NamedTupleCursor
+from   psycopg2.extensions import quote_ident
+import sys
+import hashlib
+
+parser = argparse.ArgumentParser(description='Record changes in tables')
+parser.add_argument('--dbhost')
+parser.add_argument('--dbname')
+parser.add_argument('--dbuser')
+parser.add_argument('--schema', default='public')
+
+a = parser.parse_args()
+
+conn = ""
+if a.dbhost:
+    conn += "host='%s' " % a.dbhost
+if a.dbname:
+    conn += "dbname='%s' " % a.dbname
+if a.dbuser:
+    conn += "user='%s' " % a.dbuser
+db = psycopg2.connect(conn)
+csr = db.cursor(cursor_factory=NamedTupleCursor)
+
+# Create table if necessary
+audit_table = quote_ident(a.schema, csr) + ".changed_tables"
+try:
+    csr.execute("select * from " + audit_table)
+    csr.fetchone()
+except Exception as e:
+    db.rollback()
+    csr.execute("create table " + audit_table +
+                """
+                (
+                    id serial,
+                    table_schema text,
+                    table_name text,
+                    ts timestamptz,
+                    sha256 text
+                )
+                """
+        )
+    db.commit()
+
+csr.execute("select * from information_schema.tables where table_schema = %s", (a.schema,))
+
+for table in csr.fetchall():
+    print(table.table_schema, table.table_name, end="", flush=True)
+    q = "select * from " + quote_ident(table.table_schema, csr) + "." + quote_ident(table.table_name, csr)
+    hash = hashlib.sha256()
+    csr = db.cursor()
+    csr.execute(q)
+    for r in csr:
+        r_bytes = ("\N{US}".join(map(lambda x: str(x), r)) + "\N{RS}").encode()
+        hash.update(r_bytes)
+    digest = hash.hexdigest()
+    csr = db.cursor(cursor_factory=NamedTupleCursor)
+    q = """
+        with m as (
+            select table_schema, table_name, max(ts) as ts
+            from {audit_table}
+            where table_schema=%(table_schema)s and table_name=%(table_name)s
+            group by table_schema, table_name
+        )
+        select * from {audit_table} natural join m
+        """.format(audit_table=audit_table)
+    csr.execute(q, {"table_schema": table.table_schema, "table_name": table.table_name})
+    old = csr.fetchone()
+    if not old or old.sha256 != digest:
+        print(" changed", digest, end="")
+        q = "insert into {audit_table}(table_schema, table_name, ts, sha256) values(%s, %s, now(), %s)".format(audit_table=audit_table)
+        csr.execute(q, (table.table_schema, table.table_name, digest))
+        db.commit()
+    db.rollback() # to close transaction
+    print(flush=True)
+
+# vim: tw=99