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Add C comment about problems with CHAR() space trimming

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This commit is contained in:
Bruce Momjian 2014-02-13 21:45:57 -05:00
parent b8f00a46bc
commit 9c57d11fca
1 changed files with 12 additions and 0 deletions
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12
src/backend/utils/adt/varchar.c
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@ -846,6 +846,18 @@ bpcharcmp(PG_FUNCTION_ARGS)
len2;
int cmp;
/*
* Trimming trailing spaces off of both strings can cause a string
* with a character less than a space to compare greater than a
* space-extended string, e.g. this returns false:
* SELECT E'ab\n'::CHAR(10) < E'ab '::CHAR(10);
* even though '\n' is less than the space if CHAR(10) was
* space-extended. The correct solution would be to trim only
* the longer string to be the same length of the shorter, if
* possible, then do the comparison. However, changing this
* might break existing indexes, breaking binary upgrades.
* For details, see http://www.postgresql.org/message-id/CAK+WP1xdmyswEehMuetNztM4H199Z1w9KWRHVMKzyyFM+hV=zA@mail.gmail.com
*/
len1 = bcTruelen(arg1);
len2 = bcTruelen(arg2);