PGPRO-17631: Remove support for 18+ versions.

Revert "PGPRO-12044: Use str_tolower instead of removed lowerstr and lowerstr_with_len."
This reverts commit 56c47f0.

Partially revert "PGPRO-10866: Use const decoration to avoid warnings:" related to
d5f139cb6814f0af2d2e1106899361e45c305630 (PostgeSQL)

Limit supported PostgreSQL versions to 17 in readme.

Tags: shared_ispell

Author: antamel

README.md

@@ -19,7 +19,7 @@ Install
 
 Before build and install `shared_ispell` you should ensure following:
 
-* PostgreSQL version is 9.6 or later.
+* PostgreSQL version is from 9.6 to 17 [^1]
 
 Installing the extension is quite simple. In that case all you need to do is this:
 
@@ -154,4 +154,9 @@ but there is not related code in the GitHub.
 
 Author
 ------
-Tomas Vondra [GitHub](https://github.com/tvondra)
+Tomas Vondra [GitHub](https://github.com/tvondra)
+
+Notes
+------
+
+[^1]: If you would like support for newer versions, please contact us: mailto:info@postgrespro.ru?subject=shared_ispell

src/shared_ispell.c

@@ -54,10 +54,8 @@
 #include "storage/ipc.h"
 #include "storage/shmem.h"
 
-#include "catalog/pg_collation_d.h"
 #include "commands/defrem.h"
 #include "tsearch/ts_locale.h"
-#include "utils/formatting.h"
 #include "access/htup_details.h"
 #include "funcapi.h"
 #include "utils/builtins.h"
@@ -348,7 +346,7 @@ init_shared_dict(DictInfo *info, MemoryContext infoCntx,
 			dict->useFlagAliases = true;
 			dict->lenAffixData = info->dict.lenAffixData;
 			dict->nAffixData = info->dict.nAffixData;
-			dict->AffixData = (const char **) palloc0(dict->nAffixData * sizeof(char *));
+			dict->AffixData = (char **) palloc0(dict->nAffixData * sizeof(char *));
 
 			for (i = 0; i < dict->nAffixData; i++)
 				dict->AffixData[i] = pstrdup(info->dict.AffixData[i]);
@@ -394,7 +392,7 @@ init_shared_dict(DictInfo *info, MemoryContext infoCntx,
 		{
 			StopList	stoplist;
 
-			readstoplist(stopFile, &stoplist, str_tolower);
+			readstoplist(stopFile, &stoplist, lowerstr);
 
 			size = sizeStopList(&stoplist, stopFile);
 			if (size > segment_info->available)
@@ -612,7 +610,7 @@ dispell_lexize(PG_FUNCTION_ARGS)
 	if (len <= 0)
 		PG_RETURN_POINTER(NULL);
 
-	txt = str_tolower(in, len, DEFAULT_COLLATION_OID);
+	txt = lowerstr_with_len(in, len);
 
 	/* need to lock the segment in shared mode */
 	LWLockAcquire(segment_info->lock, LW_SHARED);
@@ -820,7 +818,7 @@ copyIspellDict(IspellDict *dict, char *dictFile, char *affixFile, int size, int
 
 	/* copy affix data */
 	copy->dict.nAffixData = dict->nAffixData;
-	copy->dict.AffixData = (const char **) shalloc(sizeof(char *) * dict->nAffixData);
+	copy->dict.AffixData = (char **) shalloc(sizeof(char *) * dict->nAffixData);
 	for (i = 0; i < copy->dict.nAffixData; i++)
 		copy->dict.AffixData[i] = shstrcpy(dict->AffixData[i]);