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commit    3397c67272e26b0cda172db1f820a5c4a6aec8d6
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Mon Apr 16 20:06:47 2018 +0000
First released in: 11.0, 9.3.23, 9.4.18, 9.5.13, 9.6.9, 10.4

    Fix broken collation-aware searches in SP-GiST text opclass.
    
    spg_text_leaf_consistent() supposed that it should compare only
    Min(querylen, entrylen) bytes of the two strings, and then deal with
    any excess bytes in one string or the other by assuming the longer
    string is greater if the prefixes are equal.  Quite aside from the
    fact that that's just wrong in some locales (e.g., 'ch' is not less
    than 'd' in cs_CZ), it also risked passing incomplete multibyte
    characters to strcoll(), with ensuing bad results.
    
    Instead, just pass the full strings to varstr_cmp, and let it decide
    what to do about unequal-length strings.
    
    Fortunately, this error doesn't imply any index corruption, it's just
    that searches might return the wrong set of entries.
    
    Per report from Emre Hasegeli, though this is not his patch.
    Thanks to Peter Geoghegan for review and discussion.
    
    This code was born broken, so back-patch to all supported branches.
    In HEAD, I failed to resist the temptation to do a bit of cosmetic
    cleanup/pgindent'ing on 710d90da1, too.
    
    Discussion: https://postgr.es/m/CAE2gYzzb6K51VnTq5i5p52z+j9p2duEa-K1T3RrC_GQEynAKEg@mail.gmail.com


 src/backend/access/spgist/spgtextproc.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/backend/access/spgist/spgtextproc.c b/src/backend/access/spgist/spgtextproc.c
index 53f298b6c2f..657efeaab01 100644
--- a/src/backend/access/spgist/spgtextproc.c
+++ b/src/backend/access/spgist/spgtextproc.c
@@ -613,22 +613,22 @@ spg_text_leaf_consistent(PG_FUNCTION_ARGS)
 			/* If asserts enabled, verify encoding of reconstructed string */
 			Assert(pg_verifymbstr(fullValue, fullLen, false));
 
-			r = varstr_cmp(fullValue, Min(queryLen, fullLen),
-						   VARDATA_ANY(query), Min(queryLen, fullLen),
+			r = varstr_cmp(fullValue, fullLen,
+						   VARDATA_ANY(query), queryLen,
 						   PG_GET_COLLATION());
 		}
 		else
 		{
 			/* Non-collation-aware comparison */
 			r = memcmp(fullValue, VARDATA_ANY(query), Min(queryLen, fullLen));
-		}
 
-		if (r == 0)
-		{
-			if (queryLen > fullLen)
-				r = -1;
-			else if (queryLen < fullLen)
-				r = 1;
+			if (r == 0)
+			{
+				if (queryLen > fullLen)
+					r = -1;
+				else if (queryLen < fullLen)
+					r = 1;
+			}
 		}
 
 		switch (strategy)


[parent: 16d3dbe2f30a]