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seg: Fix seg_out() to preserve the upper boundary's certainty indicator

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When printing the upper boundary of a seg interval, seg_out() decided
whether to emit the certainty indicator ('<', '>' or '~') by testing the
upper indicator (u_ext) for '<' and '>', but mistakenly tested the lower
indicator (l_ext) for '~'.  This is a copy-and-paste slip from the
symmetric code that prints the lower boundary a few lines above.

The consequences for valid input were:

  * A '~' on the upper boundary was dropped on output, e.g.
    '1.5 .. ~2.5'::seg printed as '1.5 .. 2.5'.

  * When the lower boundary carried '~' but the upper boundary had no
    indicator, the wrong test matched and sprintf(p, "%c", seg->u_ext)
    wrote a NUL byte (u_ext == '\0'), which truncated the result string
    and silently lost the entire upper boundary, e.g.
    '~6.5 .. 8.5'::seg printed as '~6.5 .. '.

Certainty indicators are documented to be preserved on output (they are
ignored by the operators, but kept as comments), so this broke the
input/output round-trip for the affected values.

The bug has existed since seg was added.  It went unnoticed because the
existing regression tests only exercised certainty indicators on
single-point segs, which are printed by a different branch of seg_out().
Add tests that place indicators on both boundaries of an interval.

Author: Ewan Young <kdbase.hack@gmail.com>
Discussion: https://www.postgresql.org/message-id/CAON2xHPYeRRCEVAv8XfE18KsEsEHCiYcJ5fOsoxFuMEfpxF1=g@mail.gmail.com
Backpatch-through: 14
This commit is contained in:
Heikki Linnakangas 2026-06-11 12:33:48 +03:00
parent eb4e7224a1
commit 0e1f1ed157
3 changed files with 55 additions and 3 deletions
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45
contrib/seg/expected/seg.out
View file

@ -263,7 +263,8 @@ SELECT '12.345678901234560000000000000000000000000000000000000000000000000000000
12.3457
(1 row)
-- Numbers with certainty indicators
-- Numbers and ranges with certainty indicators. Certainty indicators
-- are stored and preserved on output, but ignored by operators.
SELECT '~6.5'::seg AS seg;
seg
------
@ -300,6 +301,48 @@ SELECT '> 6.5'::seg AS seg;
>6.5
(1 row)
SELECT '~1.5 .. 2.5'::seg AS seg;
seg
-------------
~1.5 .. 2.5
(1 row)
SELECT '1.5 .. ~2.5'::seg AS seg;
seg
-------------
1.5 .. ~2.5
(1 row)
SELECT '~1.5 .. ~2.5'::seg AS seg;
seg
--------------
~1.5 .. ~2.5
(1 row)
SELECT '<1.5 .. 2.5'::seg AS seg;
seg
-------------
<1.5 .. 2.5
(1 row)
SELECT '1.5 .. <2.5'::seg AS seg;
seg
-------------
1.5 .. <2.5
(1 row)
SELECT '>1.5 .. 2.5'::seg AS seg;
seg
-------------
>1.5 .. 2.5
(1 row)
SELECT '1.5 .. >2.5'::seg AS seg;
seg
-------------
1.5 .. >2.5
(1 row)
-- Open intervals
SELECT '0..'::seg AS seg;
seg

2
contrib/seg/seg.c
View file

@ -152,7 +152,7 @@ seg_out(PG_FUNCTION_ARGS)
{
/* print the upper boundary if exists */
p += sprintf(p, " ");
if (seg->u_ext == '>' || seg->u_ext == '<' || seg->l_ext == '~')
if (seg->u_ext == '>' || seg->u_ext == '<' || seg->u_ext == '~')
p += sprintf(p, "%c", seg->u_ext);
p += restore(p, seg->upper, seg->u_sigd);
}

11
contrib/seg/sql/seg.sql
View file

@ -63,7 +63,8 @@ SELECT '12.34567890123456'::seg AS seg;
-- Same, with a very long input
SELECT '12.3456789012345600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'::seg AS seg;
-- Numbers with certainty indicators
-- Numbers and ranges with certainty indicators. Certainty indicators
-- are stored and preserved on output, but ignored by operators.
SELECT '~6.5'::seg AS seg;
SELECT '<6.5'::seg AS seg;
SELECT '>6.5'::seg AS seg;
@ -71,6 +72,14 @@ SELECT '~ 6.5'::seg AS seg;
SELECT '< 6.5'::seg AS seg;
SELECT '> 6.5'::seg AS seg;
SELECT '~1.5 .. 2.5'::seg AS seg;
SELECT '1.5 .. ~2.5'::seg AS seg;
SELECT '~1.5 .. ~2.5'::seg AS seg;
SELECT '<1.5 .. 2.5'::seg AS seg;
SELECT '1.5 .. <2.5'::seg AS seg;
SELECT '>1.5 .. 2.5'::seg AS seg;
SELECT '1.5 .. >2.5'::seg AS seg;
-- Open intervals
SELECT '0..'::seg AS seg;
SELECT '0...'::seg AS seg;