> How much bigger (in lines of code) is Postgres now versus the one from 15 years ago?

I was curious as well and wrote a, very crude, script to measure it:

  for t in $(git tag -l|grep -E 'REL.*_0$|REL[67]_[0-4]$'|grep -v REL2);do echo -ne "$t\t"; git ls-tree -r $t --object-only |xargs git show |grep -a -v '^\s+$'|wc -l;done
  REL6_1          270033
  REL6_2          320297
  REL6_3          386532
  REL7_0          630771
  REL7_1          843219
  REL7_2          986991
  REL7_3          1363668
  REL7_4          1492418
  REL8_0_0        1649775
  REL8_1_0        1702325
  REL8_2_0        1806170
  REL8_3_0        2017685
  REL8_4_0        1924918
  REL9_0_0        2011704
  REL9_1_0        2225796
  REL9_2_0        2290872
  REL9_3_0        2405598
  REL9_4_0        2487304
  REL9_5_0        2527906
  REL9_6_0        2632559
  REL_10_0        2534653
  REL_11_0        2771914
  REL_12_0        2697892
  REL_13_0        2822066
  REL_14_0        2980221
  REL_15_0        3054963
  REL_16_0        3351147

This is counting non-empty lines. It's definitely not a good measure of overall code size, as it includes things like regression tests "expected" files. But as that's true for all versions, it should still allow for a decent comparison.

8.3.0 was released 2008-02-01, with 2M non-empty lines, we're now at 3.4M.