From b47b4dbf683f13e6ef09fa0d93aa6e84f3d00819 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 3 Feb 2016 14:17:35 -0500
Subject: Extend sortsupport for text to more opclasses.
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Have varlena.c expose an interface that allows the char(n), bytea, and
bpchar types to piggyback on a now-generalized SortSupport for text.
This pushes a little more knowledge of the bpchar/char(n) type into
varlena.c than might be preferred, but that seems like the approach
that creates least friction.  Also speed things up for index builds
that use text_pattern_ops or varchar_pattern_ops.

This patch does quite a bit of renaming, but it seems likely to be
worth it, so as to avoid future confusion about the fact that this code
is now more generally used than the old names might have suggested.

Peter Geoghegan, reviewed by Álvaro Herrera and Andreas Karlsson,
with small tweaks by me.
---
 src/backend/utils/adt/varchar.c | 55 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 6 deletions(-)

(limited to 'src/backend/utils/adt/varchar.c')

diff --git a/src/backend/utils/adt/varchar.c b/src/backend/utils/adt/varchar.c
index 0498fef4049..94d6da5eb57 100644
--- a/src/backend/utils/adt/varchar.c
+++ b/src/backend/utils/adt/varchar.c
@@ -17,6 +17,7 @@
 
 #include "access/hash.h"
 #include "access/tuptoaster.h"
+#include "catalog/pg_collation.h"
 #include "libpq/pqformat.h"
 #include "nodes/nodeFuncs.h"
 #include "utils/array.h"
@@ -649,14 +650,21 @@ varchartypmodout(PG_FUNCTION_ARGS)
  *****************************************************************************/
 
 /* "True" length (not counting trailing blanks) of a BpChar */
-static int
+static inline int
 bcTruelen(BpChar *arg)
 {
-	char	   *s = VARDATA_ANY(arg);
+	return bpchartruelen(VARDATA_ANY(arg), VARSIZE_ANY_EXHDR(arg));
+}
+
+int
+bpchartruelen(char *s, int len)
+{
 	int			i;
-	int			len;
 
-	len = VARSIZE_ANY_EXHDR(arg);
+	/*
+	 * Note that we rely on the assumption that ' ' is a singleton unit on
+	 * every supported multibyte server encoding.
+	 */
 	for (i = len - 1; i >= 0; i--)
 	{
 		if (s[i] != ' ')
@@ -858,6 +866,23 @@ bpcharcmp(PG_FUNCTION_ARGS)
 	PG_RETURN_INT32(cmp);
 }
 
+Datum
+bpchar_sortsupport(PG_FUNCTION_ARGS)
+{
+	SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
+	Oid			collid = ssup->ssup_collation;
+	MemoryContext oldcontext;
+
+	oldcontext = MemoryContextSwitchTo(ssup->ssup_cxt);
+
+	/* Use generic string SortSupport */
+	varstr_sortsupport(ssup, collid, true);
+
+	MemoryContextSwitchTo(oldcontext);
+
+	PG_RETURN_VOID();
+}
+
 Datum
 bpchar_larger(PG_FUNCTION_ARGS)
 {
@@ -926,8 +951,9 @@ hashbpchar(PG_FUNCTION_ARGS)
 /*
  * The following operators support character-by-character comparison
  * of bpchar datums, to allow building indexes suitable for LIKE clauses.
- * Note that the regular bpchareq/bpcharne comparison operators are assumed
- * to be compatible with these!
+ * Note that the regular bpchareq/bpcharne comparison operators, and
+ * regular support functions 1 and 2 with "C" collation are assumed to be
+ * compatible with these!
  */
 
 static int
@@ -1030,3 +1056,20 @@ btbpchar_pattern_cmp(PG_FUNCTION_ARGS)
 
 	PG_RETURN_INT32(result);
 }
+
+
+Datum
+btbpchar_pattern_sortsupport(PG_FUNCTION_ARGS)
+{
+	SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
+	MemoryContext oldcontext;
+
+	oldcontext = MemoryContextSwitchTo(ssup->ssup_cxt);
+
+	/* Use generic string SortSupport, forcing "C" collation */
+	varstr_sortsupport(ssup, C_COLLATION_OID, true);
+
+	MemoryContextSwitchTo(oldcontext);
+
+	PG_RETURN_VOID();
+}
-- 
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