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

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

diff --git a/contrib/btree_gist/btree_bit.c b/contrib/btree_gist/btree_bit.c
index 8d8e94542681d0ae819dcc7dab151c7f9b3d128e..5fb8c8b82f0ce6e845899295810ea6eda1f5ce24 100644 (file)
--- a/contrib/btree_gist/btree_bit.c
+++ b/contrib/btree_gist/btree_bit.c
@@ -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,

diff --git a/contrib/btree_gist/btree_bytea.c b/contrib/btree_gist/btree_bytea.c
index 8411598a99b5f6aea95e93320b6537b85cb6626e..bcb469e8c86a9ba2f4e2d4a91bb7c427a0c3e1b2 100644 (file)
--- a/contrib/btree_gist/btree_bytea.c
+++ b/contrib/btree_gist/btree_bytea.c
@@ -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,

diff --git a/contrib/btree_gist/btree_numeric.c b/contrib/btree_gist/btree_numeric.c
index 8a506865b1776819230ae35950d6974ece410932..7a75e2ed00d9687b66be5d38f7f7dd6538ad1295 100644 (file)
--- a/contrib/btree_gist/btree_numeric.c
+++ b/contrib/btree_gist/btree_numeric.c
@@ -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,

diff --git a/contrib/btree_gist/btree_text.c b/contrib/btree_gist/btree_text.c
index e7269ba3e7cc595664eacff51296266fddecae95..a8657fe461ac09023a40652cb98388c13be27857 100644 (file)
--- a/contrib/btree_gist/btree_text.c
+++ b/contrib/btree_gist/btree_text.c
@@ -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);

diff --git a/contrib/btree_gist/btree_utils_var.c b/contrib/btree_gist/btree_utils_var.c
index ae1018013557047830786cb4c417e123ac3c443e..3eeaee6bc359e493034d945e0da01aadfbe998d1 100644 (file)
--- a/contrib/btree_gist/btree_utils_var.c
+++ b/contrib/btree_gist/btree_utils_var.c
@@ -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 */

diff --git a/contrib/btree_gist/btree_utils_var.h b/contrib/btree_gist/btree_utils_var.h
index d746186544b078e43c4e9e6f8556e1700d64a1e5..2ed7eaa86b2d90d39e01284372557d847cbda69f 100644 (file)
--- a/contrib/btree_gist/btree_utils_var.h
+++ b/contrib/btree_gist/btree_utils_var.h
@@ -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 */