I am just beginning the process of merging two fairly large databases. This merge is complicated by the fact that there are a number of shared tables between the two databases. To help assess the situation, I've written a short python script to generate lists of tables for each database, then find any overlap / difference.

So, if database1 had the following tables:

• table_a
• table_b
• table_c
• table_d
  

and database2 had the following tables:

• table_a
• table_c
• table_e
• table_f
  

The script would generate the following output files: Diff:

• table_b
• table_d
  

Overlap:

• table_a

• table_c

  !/usr/bin/env python

  import os, sys, re

  def diff_tables(*args): databases = list(args) db_tables = [] for db in databases: os.system('psql -c "\dt" %s > %s_tables' % (db, db)) db_file = open("%s_tables" % (db), 'r') db_lines = db_file.readlines() tables_found = [] for line in db_lines: table_name = extract_table(line) if table_name: tables_found.append(table_name) db_tables.append(tables_found) db_file.close()

  diffs = [[] for i in range(len(db_tables))]
  overlaps = [[] for i in range(len(db_tables))]
  primary_db = databases.pop(0)
  primary_tables = db_tables.pop(0)
  for table in primary_tables:
      for i in range(len(db_tables)):
          if table not in db_tables:
              diffs.append(table)
          else:
              overlaps.append(table)
  
  for i in range(len(db_tables)):
      diff_file = open('diff_%s_%s' % (primary_db, databases), 'w')
      diff_file.write('\n'.join(diffs*))
      diff_file.close()
  
      overlap_file = open('overlap_%s_%s' % (primary_db, databases), 'w')
      overlap_file.write('\n'.join(overlaps*))
      overlap_file.close()
  

  def extract_table(line): match = re.search(r'\s(public|private)\s\|\s([a-zA-Z0-9_]+)\s\|\stable\s\|.*', line) if match: return match.groups()[1] return None

  if name == 'main': cmd_args = sys.argv if len(cmd_args) < 3: print 'Find the differences in database tables, given 2 or more databases' print '----------------------------------------------------------' print 'Provide 2 or more databases as arguments: %s database1 database2' % (cmd_args[0]) else: diff_tables(cmd_args[1], *cmd_args[2:])

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