Re: postgresql.conf.sample tab width

[Nathan Bossart]

I noticed that initdb still adds tabs to postgresql.conf.  Here is a patch
to fix that, which simplifies replace_guc_value() a bit.

-- 
nathan

>From 7894bcefd428bd77c926a605b620e946a5b86ade Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nat...@postgresql.org>
Date: Sun, 30 Aug 2026 11:41:41 -0500
Subject: [PATCH v1 1/1] initdb: Pad rewritten GUC lines with spaces, not tabs.

Commit f63ae72bbc converted postgresql.conf.sample to spaces so
that it lines up at any tab width, but replace_guc_value() still
pads with tabs when it re-aligns the trailing comment of a setting
it rewrites.  The postgresql.conf that initdb generates therefore
mixes the two.

To fix, pad with spaces.  While at it, simplify the calculation of
the original comment column: with no tabs left in the sample file
or in the lines we write out in its place, the de-tab-ifying loop
is only ever counting bytes, so have it count bytes directly.

Oversight in commit f63ae72bbc.

Discussion: https://postgr.es/m/aReNUKdMgKxLqmq7%40nathan
Backpatch-through: 19
---
 src/bin/initdb/initdb.c | 31 +++++--------------------------
 1 file changed, 5 insertions(+), 26 deletions(-)

diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index b3d496372ad..86d42a98a27 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -587,37 +587,16 @@ replace_guc_value(char **lines, const char *guc_name, 
const char *guc_value,
                {
                        /*
                         * We try to preserve original indentation, which is 
tedious.
-                        * oldindent and newindent are measured in de-tab-ified 
columns.
                         */
-                       const char *ptr;
-                       int                     oldindent = 0;
-                       int                     newindent;
+                       int                     oldindent = (int) (where - 
lines[i]);
+                       int                     newindent = newline->len;
 
-                       for (ptr = lines[i]; ptr < where; ptr++)
-                       {
-                               if (*ptr == '\t')
-                                       oldindent += 8 - (oldindent % 8);
-                               else
-                                       oldindent++;
-                       }
-                       /* ignore the possibility of tabs in guc_value */
-                       newindent = newline->len;
-                       /* append appropriate tabs and spaces, forcing at least 
one */
+                       /* append appropriate spaces, forcing at least one */
                        oldindent = Max(oldindent, newindent + 1);
                        while (newindent < oldindent)
                        {
-                               int                     newindent_if_tab = 
newindent + 8 - (newindent % 8);
-
-                               if (newindent_if_tab <= oldindent)
-                               {
-                                       appendPQExpBufferChar(newline, '\t');
-                                       newindent = newindent_if_tab;
-                               }
-                               else
-                               {
-                                       appendPQExpBufferChar(newline, ' ');
-                                       newindent++;
-                               }
+                               appendPQExpBufferChar(newline, ' ');
+                               newindent++;
                        }
                        /* and finally append the old comment */
                        appendPQExpBufferStr(newline, where);
-- 
2.55.0