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Commit54b1cb7

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Fix results of index-only scans on btree_gist char(N) indexes.
If contrib/btree_gist is used to make a GIST index on a char(N)(bpchar) column, and that column is retrieved via an index-onlyscan, what came out had all trailing spaces removed. Sincethat doesn't happen in any other kind of table scan, this isclearly a bug. The cause is that gbt_bpchar_compress() stripstrailing spaces (using rtrim1) before a new index entry is made.That was probably a good idea when this code was first written,but since we invented index-only scans, it's not so good.One answer could be to mark this opclass as incapable of index-onlyscans. But to do so, we'd need an extension module version bump,followed by manual action by DBAs to install the updated versionof btree_gist. And it's not really a desirable place to end up,anyway.Instead, let's fix the code by removing the unwanted space-strippingaction and adjusting the opclass's comparison logic to ignoretrailing spaces as bpchar normally does. This will not hindercases that work today, since index searches with this logic willact the same whether trailing spaces are stored or not. It willnot by itself fix the problem of getting space-stripped resultsfrom index-only scans, of course. Users who care about that canREINDEX affected indexes after installing this update, to immediatelyreplace all improperly-truncated index entries. Otherwise, it canbe expected that the index's behavior will change incrementally asold entries are replaced by new ones.Per report from Alexander Lakhin. Back-patch to all supported branches.Discussion:https://postgr.es/m/696c995b-b37f-5526-f45d-04abe713179f@gmail.com
1 parentf1e9085 commit54b1cb7

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3 files changed

+82
-34
lines changed

3 files changed

+82
-34
lines changed

‎contrib/btree_gist/btree_text.c

Lines changed: 76 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -90,6 +90,76 @@ static gbtree_vinfo tinfo =
9090
NULL
9191
};
9292

93+
/* bpchar needs its own comparison rules */
94+
95+
staticbool
96+
gbt_bpchargt(constvoid*a,constvoid*b,Oidcollation,FmgrInfo*flinfo)
97+
{
98+
returnDatumGetBool(DirectFunctionCall2Coll(bpchargt,
99+
collation,
100+
PointerGetDatum(a),
101+
PointerGetDatum(b)));
102+
}
103+
104+
staticbool
105+
gbt_bpcharge(constvoid*a,constvoid*b,Oidcollation,FmgrInfo*flinfo)
106+
{
107+
returnDatumGetBool(DirectFunctionCall2Coll(bpcharge,
108+
collation,
109+
PointerGetDatum(a),
110+
PointerGetDatum(b)));
111+
}
112+
113+
staticbool
114+
gbt_bpchareq(constvoid*a,constvoid*b,Oidcollation,FmgrInfo*flinfo)
115+
{
116+
returnDatumGetBool(DirectFunctionCall2Coll(bpchareq,
117+
collation,
118+
PointerGetDatum(a),
119+
PointerGetDatum(b)));
120+
}
121+
122+
staticbool
123+
gbt_bpcharle(constvoid*a,constvoid*b,Oidcollation,FmgrInfo*flinfo)
124+
{
125+
returnDatumGetBool(DirectFunctionCall2Coll(bpcharle,
126+
collation,
127+
PointerGetDatum(a),
128+
PointerGetDatum(b)));
129+
}
130+
131+
staticbool
132+
gbt_bpcharlt(constvoid*a,constvoid*b,Oidcollation,FmgrInfo*flinfo)
133+
{
134+
returnDatumGetBool(DirectFunctionCall2Coll(bpcharlt,
135+
collation,
136+
PointerGetDatum(a),
137+
PointerGetDatum(b)));
138+
}
139+
140+
staticint32
141+
gbt_bpcharcmp(constvoid*a,constvoid*b,Oidcollation,FmgrInfo*flinfo)
142+
{
143+
returnDatumGetInt32(DirectFunctionCall2Coll(bpcharcmp,
144+
collation,
145+
PointerGetDatum(a),
146+
PointerGetDatum(b)));
147+
}
148+
149+
staticgbtree_vinfobptinfo=
150+
{
151+
gbt_t_bpchar,
152+
0,
153+
false,
154+
gbt_bpchargt,
155+
gbt_bpcharge,
156+
gbt_bpchareq,
157+
gbt_bpcharle,
158+
gbt_bpcharlt,
159+
gbt_bpcharcmp,
160+
NULL
161+
};
162+
93163

94164
/**************************************************
95165
* Text ops
@@ -112,29 +182,8 @@ gbt_text_compress(PG_FUNCTION_ARGS)
112182
Datum
113183
gbt_bpchar_compress(PG_FUNCTION_ARGS)
114184
{
115-
GISTENTRY*entry= (GISTENTRY*)PG_GETARG_POINTER(0);
116-
GISTENTRY*retval;
117-
118-
if (tinfo.eml==0)
119-
{
120-
tinfo.eml=pg_database_encoding_max_length();
121-
}
122-
123-
if (entry->leafkey)
124-
{
125-
126-
Datumd=DirectFunctionCall1(rtrim1,entry->key);
127-
GISTENTRYtrim;
128-
129-
gistentryinit(trim,d,
130-
entry->rel,entry->page,
131-
entry->offset, true);
132-
retval=gbt_var_compress(&trim,&tinfo);
133-
}
134-
else
135-
retval=entry;
136-
137-
PG_RETURN_POINTER(retval);
185+
/* This should never have been distinct from gbt_text_compress */
186+
returngbt_text_compress(fcinfo);
138187
}
139188

140189

@@ -179,18 +228,17 @@ gbt_bpchar_consistent(PG_FUNCTION_ARGS)
179228
boolretval;
180229
GBT_VARKEY*key= (GBT_VARKEY*)DatumGetPointer(entry->key);
181230
GBT_VARKEY_Rr=gbt_var_key_readable(key);
182-
void*trim= (void*)DatumGetPointer(DirectFunctionCall1(rtrim1,PointerGetDatum(query)));
183231

184232
/* All cases served by this function are exact */
185233
*recheck= false;
186234

187-
if (tinfo.eml==0)
235+
if (bptinfo.eml==0)
188236
{
189-
tinfo.eml=pg_database_encoding_max_length();
237+
bptinfo.eml=pg_database_encoding_max_length();
190238
}
191239

192-
retval=gbt_var_consistent(&r,trim,strategy,PG_GET_COLLATION(),
193-
GIST_LEAF(entry),&tinfo,fcinfo->flinfo);
240+
retval=gbt_var_consistent(&r,query,strategy,PG_GET_COLLATION(),
241+
GIST_LEAF(entry),&bptinfo,fcinfo->flinfo);
194242
PG_RETURN_BOOL(retval);
195243
}
196244

‎contrib/btree_gist/expected/char.out

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -75,8 +75,8 @@ SELECT * FROM chartmp WHERE a BETWEEN '31a' AND '31c';
7575
(2 rows)
7676

7777
SELECT * FROM chartmp WHERE a BETWEEN '31a' AND '31c';
78-
a
79-
------
80-
31b0
78+
a
79+
----------------------------------
80+
31b0
8181
(1 row)
8282

‎contrib/btree_gist/expected/char_1.out

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -75,8 +75,8 @@ SELECT * FROM chartmp WHERE a BETWEEN '31a' AND '31c';
7575
(2 rows)
7676

7777
SELECT * FROM chartmp WHERE a BETWEEN '31a' AND '31c';
78-
a
79-
------
80-
31b0
78+
a
79+
----------------------------------
80+
31b0
8181
(1 row)
8282

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