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Remove btree_gist's useless logic for encoding-aware truncation.

Browse source 
gbt_var_node_cp_len() contained logic to ensure that its choice of
a common prefix length didn't truncate away part of a multibyte
character.  However, that was really dead code, because we have not
allowed truncation of text-string data types since ef770cbb6, and
it seems unlikely that that behavior could ever get resurrected.
The code is still reachable via gbt_var_penalty, but for that
usage it hardly matters if we break in the middle of a multibyte
character: we're just calculating a small correction factor that
is arguably bunkum anyway in non-C locales.

Hence, delete said code.  That actually removes all need for
gbtree_vinfo.eml, which allows const-ification of the gbtree_vinfo
structs in which we were changing it, which removes one headache
for future attempts to thread-ify the backend.

(Curiously, all this infrastructure was itself added by ef770cbb6.
Not sure why Teodor didn't see the contradiction.)

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
Discussion: https://postgr.es/m/AH*AvQCYKhQGVvPWi1GiU4oY.8.1781609375063.Hmail.3020001251@tju.edu.cn
This commit is contained in:
Tom Lane 2026-07-03 15:31:58 -04:00
parent fea9c1884b
commit b82d69abf6
6 changed files with 8 additions and 55 deletions
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1
contrib/btree_gist/btree_bit.c
View file

@ -136,7 +136,6 @@ gbt_bit_l2n(GBT_VARKEY *leaf, FmgrInfo *flinfo)
static const gbtree_vinfo tinfo =
{
gbt_t_bit,
0,
true, /* internal keys can be truncated */
gbt_bitgt,
gbt_bitge,

1
contrib/btree_gist/btree_bytea.c
View file

@ -73,7 +73,6 @@ gbt_byteacmp(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
static const gbtree_vinfo tinfo =
{
gbt_t_bytea,
0,
true, /* internal keys can be truncated */
gbt_byteagt,
gbt_byteage,

1
contrib/btree_gist/btree_numeric.c
View file

@ -83,7 +83,6 @@ gbt_numeric_cmp(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
static const gbtree_vinfo tinfo =
{
gbt_t_numeric,
0,
false, /* no truncation permitted */
gbt_numeric_gt,
gbt_numeric_ge,

21
contrib/btree_gist/btree_text.c
View file

@ -86,10 +86,9 @@ gbt_textcmp(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
* more complicated than C. The prefix-match hack used for simpler types
* can't fix it, either.
*/
static gbtree_vinfo tinfo =
static const gbtree_vinfo tinfo =
{
gbt_t_text,
0,
false, /* no truncation permitted */
gbt_textgt,
gbt_textge,
@ -156,10 +155,9 @@ gbt_bpcharcmp(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
PointerGetDatum(b)));
}
static gbtree_vinfo bptinfo =
static const gbtree_vinfo bptinfo =
{
gbt_t_bpchar,
0,
false, /* as above, no truncation permitted */
gbt_bpchargt,
gbt_bpcharge,
@ -180,11 +178,6 @@ gbt_text_compress(PG_FUNCTION_ARGS)
{
GISTENTRY *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
if (tinfo.eml == 0)
{
tinfo.eml = pg_database_encoding_max_length();
}
PG_RETURN_POINTER(gbt_var_compress(entry, &tinfo));
}
@ -212,11 +205,6 @@ gbt_text_consistent(PG_FUNCTION_ARGS)
/* All cases served by this function are exact */
*recheck = false;
if (tinfo.eml == 0)
{
tinfo.eml = pg_database_encoding_max_length();
}
retval = gbt_var_consistent(&r, query, strategy, PG_GET_COLLATION(),
GIST_LEAF(entry), &tinfo, fcinfo->flinfo);
@ -240,11 +228,6 @@ gbt_bpchar_consistent(PG_FUNCTION_ARGS)
/* All cases served by this function are exact */
*recheck = false;
if (bptinfo.eml == 0)
{
bptinfo.eml = pg_database_encoding_max_length();
}
retval = gbt_var_consistent(&r, query, strategy, PG_GET_COLLATION(),
GIST_LEAF(entry), &bptinfo, fcinfo->flinfo);
PG_RETURN_BOOL(retval);

37
contrib/btree_gist/btree_utils_var.c
View file

@ -10,7 +10,6 @@
#include "btree_gist.h"
#include "btree_utils_var.h"
#include "mb/pg_wchar.h"
#include "utils/rel.h"
#include "varatt.h"
@ -126,56 +125,32 @@ gbt_var_leaf2node(GBT_VARKEY *leaf, const gbtree_vinfo *tinfo, FmgrInfo *flinfo)
/*
* returns the common prefix length of a node key
*
* If the underlying type is character data, the prefix length may point in
* the middle of a multibyte character.
* This is not used for any cases where the underlying type is character data
* (except in gbt_var_penalty, where it doesn't matter since we're just making
* an estimated correction not constructing a truncated string). If it were,
* we'd need to be careful not to truncate in the middle of a multibyte
* character.
*/
static int32
gbt_var_node_cp_len(const GBT_VARKEY *node, const gbtree_vinfo *tinfo)
{
GBT_VARKEY_R r = gbt_var_key_readable(node);
int32 i = 0;
int32 l_left_to_match = 0;
int32 l_total = 0;
int32 t1len = VARSIZE(r.lower) - VARHDRSZ;
int32 t2len = VARSIZE(r.upper) - VARHDRSZ;
int32 ml = Min(t1len, t2len);
char *p1 = VARDATA(r.lower);
char *p2 = VARDATA(r.upper);
const char *end1 = p1 + t1len;
const char *end2 = p2 + t2len;
if (ml == 0)
return 0;
while (i < ml)
{
if (tinfo->eml > 1 && l_left_to_match == 0)
{
l_total = pg_mblen_range(p1, end1);
if (l_total != pg_mblen_range(p2, end2))
{
return i;
}
l_left_to_match = l_total;
}
if (*p1 != *p2)
{
if (tinfo->eml > 1)
{
int32 l_matched_subset = l_total - l_left_to_match;
/* end common prefix at final byte of last matching char */
return i - l_matched_subset;
}
else
{
return i;
}
}
return i;
p1++;
p2++;
l_left_to_match--;
i++;
}
return ml; /* lower == upper */

2
contrib/btree_gist/btree_utils_var.h
View file

@ -60,8 +60,6 @@ typedef struct
/* Attribs */
enum gbtree_type t; /* data type */
int32 eml; /* cached pg_database_encoding_max_length (0:
* undefined) */
bool trnc; /* truncate (=compress) key */
/* Methods */