Make various variables const (read-only).

These changes should generally improve correctness/maintainability.
A nice side benefit is that several kilobytes move from initialized
data to text segment, allowing them to be shared across processes and
probably reducing copy-on-write overhead while forking a new backend.
Unfortunately this doesn't seem to help libpq in the same way (at least
not when it's compiled with -fpic on x86_64), but we can hope the linker
at least collects all nominally-const data together even if it's not
actually part of the text segment.

Also, make pg_encname_tbl[] static in encnames.c, since there seems
no very good reason for any other code to use it; per a suggestion
from Wim Lewis, who independently submitted a patch that was mostly
a subset of this one.

Oskari Saarenmaa, with some editorialization by me

16 files changed, 101 insertions, 130 deletions

diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index f8fd4f8c469..991c02abbf1 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -101,7 +101,7 @@ typedef struct
 										 * class? */
 } ObjectPropertyType;
 
-static ObjectPropertyType ObjectProperty[] =
+static const ObjectPropertyType ObjectProperty[] =
 {
 	{
 		CastRelationId,
@@ -431,7 +431,7 @@ static ObjectAddress get_object_address_type(ObjectType objtype,
 						List *objname, bool missing_ok);
 static ObjectAddress get_object_address_opcf(ObjectType objtype, List *objname,
 						List *objargs, bool missing_ok);
-static ObjectPropertyType *get_object_property_data(Oid class_id);
+static const ObjectPropertyType *get_object_property_data(Oid class_id);
 
 static void getRelationDescription(StringInfo buffer, Oid relid);
 static void getOpFamilyDescription(StringInfo buffer, Oid opfid);
@@ -1297,7 +1297,7 @@ get_object_namespace(const ObjectAddress *address)
 	HeapTuple	tuple;
 	bool		isnull;
 	Oid			oid;
-	ObjectPropertyType *property;
+	const ObjectPropertyType *property;
 
 	/* If not owned by a namespace, just return InvalidOid. */
 	property = get_object_property_data(address->classId);
@@ -1329,7 +1329,7 @@ get_object_namespace(const ObjectAddress *address)
 Oid
 get_object_oid_index(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->oid_index_oid;
 }
@@ -1337,7 +1337,7 @@ get_object_oid_index(Oid class_id)
 int
 get_object_catcache_oid(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->oid_catcache_id;
 }
@@ -1345,7 +1345,7 @@ get_object_catcache_oid(Oid class_id)
 int
 get_object_catcache_name(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->name_catcache_id;
 }
@@ -1353,7 +1353,7 @@ get_object_catcache_name(Oid class_id)
 AttrNumber
 get_object_attnum_name(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->attnum_name;
 }
@@ -1361,7 +1361,7 @@ get_object_attnum_name(Oid class_id)
 AttrNumber
 get_object_attnum_namespace(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->attnum_namespace;
 }
@@ -1369,7 +1369,7 @@ get_object_attnum_namespace(Oid class_id)
 AttrNumber
 get_object_attnum_owner(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->attnum_owner;
 }
@@ -1377,7 +1377,7 @@ get_object_attnum_owner(Oid class_id)
 AttrNumber
 get_object_attnum_acl(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->attnum_acl;
 }
@@ -1385,7 +1385,7 @@ get_object_attnum_acl(Oid class_id)
 AclObjectKind
 get_object_aclkind(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->acl_kind;
 }
@@ -1393,7 +1393,7 @@ get_object_aclkind(Oid class_id)
 bool
 get_object_namensp_unique(Oid class_id)
 {
-	ObjectPropertyType *prop = get_object_property_data(class_id);
+	const ObjectPropertyType *prop = get_object_property_data(class_id);
 
 	return prop->is_nsp_name_unique;
 }
@@ -1419,10 +1419,10 @@ is_objectclass_supported(Oid class_id)
 /*
  * Find ObjectProperty structure by class_id.
  */
-static ObjectPropertyType *
+static const ObjectPropertyType *
 get_object_property_data(Oid class_id)
 {
-	static ObjectPropertyType *prop_last = NULL;
+	static const ObjectPropertyType *prop_last = NULL;
 	int			index;
 
 	/*
diff --git a/src/backend/commands/conversioncmds.c b/src/backend/commands/conversioncmds.c
index f206c7bac31..dc55fe5ed44 100644
--- a/src/backend/commands/conversioncmds.c
+++ b/src/backend/commands/conversioncmds.c
@@ -46,7 +46,7 @@ CreateConversionCommand(CreateConversionStmt *stmt)
 	const char *from_encoding_name = stmt->for_encoding_name;
 	const char *to_encoding_name = stmt->to_encoding_name;
 	List	   *func_name = stmt->func_name;
-	static Oid	funcargs[] = {INT4OID, INT4OID, CSTRINGOID, INTERNALOID, INT4OID};
+	static const Oid funcargs[] = {INT4OID, INT4OID, CSTRINGOID, INTERNALOID, INT4OID};
 	char		result[1];
 
 	/* Convert list of names to a name and namespace */
diff --git a/src/backend/regex/regc_lex.c b/src/backend/regex/regc_lex.c
index 3360cfb0e9f..c4095e98cbd 100644
--- a/src/backend/regex/regc_lex.c
+++ b/src/backend/regex/regc_lex.c
@@ -716,10 +716,10 @@ static int						/* not actually used, but convenient for RETV */
 lexescape(struct vars * v)
 {
 	chr			c;
-	static chr	alert[] = {
+	static const chr alert[] = {
 		CHR('a'), CHR('l'), CHR('e'), CHR('r'), CHR('t')
 	};
-	static chr	esc[] = {
+	static const chr esc[] = {
 		CHR('E'), CHR('S'), CHR('C')
 	};
 	const chr  *save;
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index b5988a2fbc1..ca1ccc52023 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -274,7 +274,7 @@ struct vars
 
 
 /* static function list */
-static struct fns functions = {
+static const struct fns functions = {
 	rfree,						/* regfree insides */
 };
 
diff --git a/src/backend/regex/regerror.c b/src/backend/regex/regerror.c
index f6a3f2667f8..4b2573e6255 100644
--- a/src/backend/regex/regerror.c
+++ b/src/backend/regex/regerror.c
@@ -34,10 +34,10 @@
 #include "regex/regguts.h"
 
 /* unknown-error explanation */
-static char unk[] = "*** unknown regex error code 0x%x ***";
+static const char unk[] = "*** unknown regex error code 0x%x ***";
 
 /* struct to map among codes, code names, and explanations */
-static struct rerr
+static const struct rerr
 {
 	int			code;
 	const char *name;
@@ -62,7 +62,7 @@ pg_regerror(int errcode,		/* error code, or REG_ATOI or REG_ITOA */
 			char *errbuf,		/* result buffer (unless errbuf_size==0) */
 			size_t errbuf_size) /* available space in errbuf, can be 0 */
 {
-	struct rerr *r;
+	const struct rerr *r;
 	const char *msg;
 	char		convbuf[sizeof(unk) + 50];		/* 50 = plenty for int */
 	size_t		len;
diff --git a/src/backend/tsearch/wparser_def.c b/src/backend/tsearch/wparser_def.c
index 7252d3b6166..fa73dff694b 100644
--- a/src/backend/tsearch/wparser_def.c
+++ b/src/backend/tsearch/wparser_def.c
@@ -789,7 +789,7 @@ p_isspecial(TParser *prs)
 	 */
 	if (GetDatabaseEncoding() == PG_UTF8 && prs->usewide)
 	{
-		static pg_wchar strange_letter[] = {
+		static const pg_wchar strange_letter[] = {
 			/*
 			 * use binary search, so elements should be ordered
 			 */
@@ -1023,7 +1023,7 @@ p_isspecial(TParser *prs)
 			0xAA34,				/* CHAM CONSONANT SIGN RA */
 			0xAA4D				/* CHAM CONSONANT SIGN FINAL H */
 		};
-		pg_wchar   *StopLow = strange_letter,
+		const pg_wchar *StopLow = strange_letter,
 				   *StopHigh = strange_letter + lengthof(strange_letter),
 				   *StopMiddle;
 		pg_wchar	c;
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index 9e4c9829ad9..a61b40e17f9 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -59,10 +59,10 @@ const int	day_tab[2][13] =
 	{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0}
 };
 
-char	   *months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
+const char *const months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", NULL};
 
-char	   *days[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
+const char *const days[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
 "Thursday", "Friday", "Saturday", NULL};
 
 
@@ -186,7 +186,7 @@ static const datetkn datetktbl[] = {
 
 static int	szdatetktbl = sizeof datetktbl / sizeof datetktbl[0];
 
-static datetkn deltatktbl[] = {
+static const datetkn deltatktbl[] = {
 	/* text, token, lexval */
 	{"@", IGNORE_DTF, 0},		/* postgres relative prefix */
 	{DAGO, AGO, 0},				/* "ago" indicates negative time offset */
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 6ae426b77a9..27aea9cbbcb 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -122,13 +122,6 @@
 
 
 /* ----------
- * External (defined in PgSQL datetime.c (timestamp utils))
- * ----------
- */
-extern char *months[],			/* month abbreviation	*/
-		   *days[];				/* full days		*/
-
-/* ----------
  * Format parser structs
  * ----------
  */
@@ -188,12 +181,12 @@ struct FormatNode
  * Full months
  * ----------
  */
-static char *months_full[] = {
+static const char *const months_full[] = {
 	"January", "February", "March", "April", "May", "June", "July",
 	"August", "September", "October", "November", "December", NULL
 };
 
-static char *days_short[] = {
+static const char *const days_short[] = {
 	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", NULL
 };
 
@@ -226,8 +219,8 @@ static char *days_short[] = {
  * matches for BC have an odd index.  So the boolean value for BC is given by
  * taking the array index of the match, modulo 2.
  */
-static char *adbc_strings[] = {ad_STR, bc_STR, AD_STR, BC_STR, NULL};
-static char *adbc_strings_long[] = {a_d_STR, b_c_STR, A_D_STR, B_C_STR, NULL};
+static const char *const adbc_strings[] = {ad_STR, bc_STR, AD_STR, BC_STR, NULL};
+static const char *const adbc_strings_long[] = {a_d_STR, b_c_STR, A_D_STR, B_C_STR, NULL};
 
 /* ----------
  * AM / PM
@@ -253,8 +246,8 @@ static char *adbc_strings_long[] = {a_d_STR, b_c_STR, A_D_STR, B_C_STR, NULL};
  * matches for PM have an odd index.  So the boolean value for PM is given by
  * taking the array index of the match, modulo 2.
  */
-static char *ampm_strings[] = {am_STR, pm_STR, AM_STR, PM_STR, NULL};
-static char *ampm_strings_long[] = {a_m_STR, p_m_STR, A_M_STR, P_M_STR, NULL};
+static const char *const ampm_strings[] = {am_STR, pm_STR, AM_STR, PM_STR, NULL};
+static const char *const ampm_strings_long[] = {a_m_STR, p_m_STR, A_M_STR, P_M_STR, NULL};
 
 /* ----------
  * Months in roman-numeral
@@ -262,26 +255,26 @@ static char *ampm_strings_long[] = {a_m_STR, p_m_STR, A_M_STR, P_M_STR, NULL};
  *	'VIII' must have higher precedence than 'V')
  * ----------
  */
-static char *rm_months_upper[] =
+static const char *const rm_months_upper[] =
 {"XII", "XI", "X", "IX", "VIII", "VII", "VI", "V", "IV", "III", "II", "I", NULL};
 
-static char *rm_months_lower[] =
+static const char *const rm_months_lower[] =
 {"xii", "xi", "x", "ix", "viii", "vii", "vi", "v", "iv", "iii", "ii", "i", NULL};
 
 /* ----------
  * Roman numbers
  * ----------
  */
-static char *rm1[] = {"I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX", NULL};
-static char *rm10[] = {"X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC", NULL};
-static char *rm100[] = {"C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM", NULL};
+static const char *const rm1[] = {"I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX", NULL};
+static const char *const rm10[] = {"X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC", NULL};
+static const char *const rm100[] = {"C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM", NULL};
 
 /* ----------
  * Ordinal postfixes
  * ----------
  */
-static char *numTH[] = {"ST", "ND", "RD", "TH", NULL};
-static char *numth[] = {"st", "nd", "rd", "th", NULL};
+static const char *const numTH[] = {"ST", "ND", "RD", "TH", NULL};
+static const char *const numth[] = {"st", "nd", "rd", "th", NULL};
 
 /* ----------
  * Flags & Options:
@@ -525,7 +518,7 @@ do { \
  * Suffixes definition for DATE-TIME TO/FROM CHAR
  * ----------
  */
-static KeySuffix DCH_suff[] = {
+static const KeySuffix DCH_suff[] = {
 	{"FM", 2, DCH_S_FM, SUFFTYPE_PREFIX},
 	{"fm", 2, DCH_S_FM, SUFFTYPE_PREFIX},
 	{"TM", 2, DCH_S_TM, SUFFTYPE_PREFIX},
@@ -950,10 +943,10 @@ typedef struct NUMProc
  */
 static const KeyWord *index_seq_search(char *str, const KeyWord *kw,
 				 const int *index);
-static KeySuffix *suff_search(char *str, KeySuffix *suf, int type);
+static const KeySuffix *suff_search(char *str, const KeySuffix *suf, int type);
 static void NUMDesc_prepare(NUMDesc *num, FormatNode *n);
 static void parse_format(FormatNode *node, char *str, const KeyWord *kw,
-			 KeySuffix *suf, const int *index, int ver, NUMDesc *Num);
+			 const KeySuffix *suf, const int *index, int ver, NUMDesc *Num);
 
 static void DCH_to_char(FormatNode *node, bool is_interval,
 			TmToChar *in, char *out, Oid collid);
@@ -964,7 +957,7 @@ static void dump_index(const KeyWord *k, const int *index);
 static void dump_node(FormatNode *node, int max);
 #endif
 
-static char *get_th(char *num, int type);
+static const char *get_th(char *num, int type);
 static char *str_numth(char *dest, char *num, int type);
 static int	adjust_partial_year_to_2020(int year);
 static int	strspace_len(char *str);
@@ -973,8 +966,8 @@ static void from_char_set_mode(TmFromChar *tmfc, const FromCharDateMode mode);
 static void from_char_set_int(int *dest, const int value, const FormatNode *node);
 static int	from_char_parse_int_len(int *dest, char **src, const int len, FormatNode *node);
 static int	from_char_parse_int(int *dest, char **src, FormatNode *node);
-static int	seq_search(char *name, char **array, int type, int max, int *len);
-static int	from_char_seq_search(int *dest, char **src, char **array, int type, int max, FormatNode *node);
+static int	seq_search(char *name, const char *const * array, int type, int max, int *len);
+static int	from_char_seq_search(int *dest, char **src, const char *const * array, int type, int max, FormatNode *node);
 static void do_to_timestamp(text *date_txt, text *fmt,
 				struct pg_tm * tm, fsec_t *fsec);
 static char *fill_str(char *str, int c, int max);
@@ -1024,10 +1017,10 @@ index_seq_search(char *str, const KeyWord *kw, const int *index)
 	return NULL;
 }
 
-static KeySuffix *
-suff_search(char *str, KeySuffix *suf, int type)
+static const KeySuffix *
+suff_search(char *str, const KeySuffix *suf, int type)
 {
-	KeySuffix  *s;
+	const KeySuffix *s;
 
 	for (s = suf; s->name != NULL; s++)
 	{
@@ -1237,9 +1230,9 @@ NUMDesc_prepare(NUMDesc *num, FormatNode *n)
  */
 static void
 parse_format(FormatNode *node, char *str, const KeyWord *kw,
-			 KeySuffix *suf, const int *index, int ver, NUMDesc *Num)
+			 const KeySuffix *suf, const int *index, int ver, NUMDesc *Num)
 {
-	KeySuffix  *s;
+	const KeySuffix *s;
 	FormatNode *n;
 	int			node_set = 0,
 				suffix,
@@ -1401,7 +1394,7 @@ dump_node(FormatNode *node, int max)
  * type --> 0 upper, 1 lower
  * ----------
  */
-static char *
+static const char *
 get_th(char *num, int type)
 {
 	int			len = strlen(num),
@@ -2268,11 +2261,11 @@ from_char_parse_int(int *dest, char **src, FormatNode *node)
  * ----------
  */
 static int
-seq_search(char *name, char **array, int type, int max, int *len)
+seq_search(char *name, const char *const * array, int type, int max, int *len)
 {
-	char	   *p,
-			   *n,
-			  **a;
+	const char *p;
+	const char *const * a;
+	char	   *n;
 	int			last,
 				i;
 
@@ -2346,7 +2339,7 @@ seq_search(char *name, char **array, int type, int max, int *len)
  * If the string doesn't match, throw an error.
  */
 static int
-from_char_seq_search(int *dest, char **src, char **array, int type, int max,
+from_char_seq_search(int *dest, char **src, const char *const * array, int type, int max,
 					 FormatNode *node)
 {
 	int			len;
diff --git a/src/backend/utils/adt/tsrank.c b/src/backend/utils/adt/tsrank.c
index a8e07e7fbc2..c9e71c9e21d 100644
--- a/src/backend/utils/adt/tsrank.c
+++ b/src/backend/utils/adt/tsrank.c
@@ -20,7 +20,7 @@
 #include "miscadmin.h"
 
 
-static float weights[] = {0.1f, 0.2f, 0.4f, 1.0f};
+static const float weights[] = {0.1f, 0.2f, 0.4f, 1.0f};
 
 #define wpos(wep)	( w[ WEP_GETWEIGHT(wep) ] )
 
@@ -33,8 +33,8 @@ static float weights[] = {0.1f, 0.2f, 0.4f, 1.0f};
 #define RANK_NORM_RDIVRPLUS1	0x20
 #define DEF_NORM_METHOD			RANK_NO_NORM
 
-static float calc_rank_or(float *w, TSVector t, TSQuery q);
-static float calc_rank_and(float *w, TSVector t, TSQuery q);
+static float calc_rank_or(const float *w, TSVector t, TSQuery q);
+static float calc_rank_and(const float *w, TSVector t, TSQuery q);
 
 /*
  * Returns a weight of a word collocation
@@ -202,7 +202,7 @@ static WordEntryPosVector POSNULL = {
 };
 
 static float
-calc_rank_and(float *w, TSVector t, TSQuery q)
+calc_rank_and(const float *w, TSVector t, TSQuery q)
 {
 	WordEntryPosVector **pos;
 	int			i,
@@ -278,7 +278,7 @@ calc_rank_and(float *w, TSVector t, TSQuery q)
 }
 
 static float
-calc_rank_or(float *w, TSVector t, TSQuery q)
+calc_rank_or(const float *w, TSVector t, TSQuery q)
 {
 	WordEntry  *entry,
 			   *firstentry;
@@ -347,7 +347,7 @@ calc_rank_or(float *w, TSVector t, TSQuery q)
 }
 
 static float
-calc_rank(float *w, TSVector t, TSQuery q, int32 method)
+calc_rank(const float *w, TSVector t, TSQuery q, int32 method)
 {
 	QueryItem  *item = GETQUERY(q);
 	float		res = 0.0;
@@ -387,7 +387,7 @@ calc_rank(float *w, TSVector t, TSQuery q, int32 method)
 	return res;
 }
 
-static float *
+static const float *
 getWeights(ArrayType *win)
 {
 	static float ws[lengthof(weights)];
@@ -723,7 +723,7 @@ get_docrep(TSVector txt, QueryRepresentation *qr, int *doclen)
 }
 
 static float4
-calc_rank_cd(float4 *arrdata, TSVector txt, TSQuery query, int method)
+calc_rank_cd(const float4 *arrdata, TSVector txt, TSQuery query, int method)
 {
 	DocRepresentation *doc;
 	int			len,
diff --git a/src/backend/utils/mb/encnames.c b/src/backend/utils/mb/encnames.c
index 772d4a5d056..38fae001eb2 100644
--- a/src/backend/utils/mb/encnames.c
+++ b/src/backend/utils/mb/encnames.c
@@ -29,7 +29,13 @@
  * Karel Zak, Aug 2001
  * ----------
  */
-pg_encname	pg_encname_tbl[] =
+typedef struct pg_encname
+{
+	const char *name;
+	pg_enc		encoding;
+} pg_encname;
+
+static const pg_encname pg_encname_tbl[] =
 {
 	{
 		"abc", PG_WIN1258
@@ -285,15 +291,9 @@ pg_encname	pg_encname_tbl[] =
 	},							/* alias for UHC */
 	{
 		"windows950", PG_BIG5
-	},							/* alias for BIG5 */
-	{
-		NULL, 0
-	}							/* last */
+	}							/* alias for BIG5 */
 };
 
-unsigned int pg_encname_tbl_sz = \
-sizeof(pg_encname_tbl) / sizeof(pg_encname_tbl[0]) - 1;
-
 /* ----------
  * These are "official" encoding names.
  * XXX must be sorted by the same order as enum pg_enc (in mb/pg_wchar.h)
@@ -304,7 +304,7 @@ sizeof(pg_encname_tbl) / sizeof(pg_encname_tbl[0]) - 1;
 #else
 #define DEF_ENC2NAME(name, codepage) { #name, PG_##name, codepage }
 #endif
-pg_enc2name pg_enc2name_tbl[] =
+const pg_enc2name pg_enc2name_tbl[] =
 {
 	DEF_ENC2NAME(SQL_ASCII, 0),
 	DEF_ENC2NAME(EUC_JP, 20932),
@@ -356,7 +356,7 @@ pg_enc2name pg_enc2name_tbl[] =
  * This covers all encodings except MULE_INTERNAL, which is alien to gettext.
  * ----------
  */
-pg_enc2gettext pg_enc2gettext_tbl[] =
+const pg_enc2gettext pg_enc2gettext_tbl[] =
 {
 	{PG_SQL_ASCII, "US-ASCII"},
 	{PG_UTF8, "UTF-8"},
@@ -467,13 +467,15 @@ clean_encoding_name(const char *key, char *newkey)
 
 /* ----------
  * Search encoding by encoding name
+ *
+ * Returns encoding ID, or -1 for error
  * ----------
  */
-pg_encname *
-pg_char_to_encname_struct(const char *name)
+int
+pg_char_to_encoding(const char *name)
 {
-	unsigned int nel = pg_encname_tbl_sz;
-	pg_encname *base = pg_encname_tbl,
+	unsigned int nel = lengthof(pg_encname_tbl);
+	const pg_encname *base = pg_encname_tbl,
 			   *last = base + nel - 1,
 			   *position;
 	int			result;
@@ -481,13 +483,13 @@ pg_char_to_encname_struct(const char *name)
 			   *key;
 
 	if (name == NULL || *name == '\0')
-		return NULL;
+		return -1;
 
 	if (strlen(name) >= NAMEDATALEN)
 	{
 #ifdef FRONTEND
 		fprintf(stderr, "encoding name too long\n");
-		return NULL;
+		return -1;
 #else
 		ereport(ERROR,
 				(errcode(ERRCODE_NAME_TOO_LONG),
@@ -505,29 +507,14 @@ pg_char_to_encname_struct(const char *name)
 		{
 			result = strcmp(key, position->name);
 			if (result == 0)
-				return position;
+				return position->encoding;
 		}
 		if (result < 0)
 			last = position - 1;
 		else
 			base = position + 1;
 	}
-	return NULL;
-}
-
-/*
- * Returns encoding or -1 for error
- */
-int
-pg_char_to_encoding(const char *name)
-{
-	pg_encname *p;
-
-	if (!name)
-		return -1;
-
-	p = pg_char_to_encname_struct(name);
-	return p ? p->encoding : -1;
+	return -1;
 }
 
 #ifndef FRONTEND
@@ -545,7 +532,7 @@ pg_encoding_to_char(int encoding)
 {
 	if (PG_VALID_ENCODING(encoding))
 	{
-		pg_enc2name *p = &pg_enc2name_tbl[encoding];
+		const pg_enc2name *p = &pg_enc2name_tbl[encoding];
 
 		Assert(encoding == p->encoding);
 		return p->name;
diff --git a/src/backend/utils/mb/mbutils.c b/src/backend/utils/mb/mbutils.c
index 6d1cd8e8759..08440e9fe9d 100644
--- a/src/backend/utils/mb/mbutils.c
+++ b/src/backend/utils/mb/mbutils.c
@@ -55,9 +55,9 @@ static FmgrInfo *ToClientConvProc = NULL;
 /*
  * These variables track the currently-selected encodings.
  */
-static pg_enc2name *ClientEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
-static pg_enc2name *DatabaseEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
-static pg_enc2name *MessageEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
+static const pg_enc2name *ClientEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
+static const pg_enc2name *DatabaseEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
+static const pg_enc2name *MessageEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
 
 /*
  * During backend startup we can't set client encoding because we (a)
diff --git a/src/backend/utils/mb/wchar.c b/src/backend/utils/mb/wchar.c
index 45bc3c1604b..6d03a10854e 100644
--- a/src/backend/utils/mb/wchar.c
+++ b/src/backend/utils/mb/wchar.c
@@ -1720,7 +1720,7 @@ pg_eucjp_increment(unsigned char *charptr, int length)
  * XXX must be sorted by the same order as enum pg_enc (in mb/pg_wchar.h)
  *-------------------------------------------------------------------
  */
-pg_wchar_tbl pg_wchar_table[] = {
+const pg_wchar_tbl pg_wchar_table[] = {
 	{pg_ascii2wchar_with_len, pg_wchar2single_with_len, pg_ascii_mblen, pg_ascii_dsplen, pg_ascii_verifier, 1}, /* PG_SQL_ASCII */
 	{pg_eucjp2wchar_with_len, pg_wchar2euc_with_len, pg_eucjp_mblen, pg_eucjp_dsplen, pg_eucjp_verifier, 3},	/* PG_EUC_JP */
 	{pg_euccn2wchar_with_len, pg_wchar2euc_with_len, pg_euccn_mblen, pg_euccn_dsplen, pg_euccn_verifier, 2},	/* PG_EUC_CN */
diff --git a/src/common/relpath.c b/src/common/relpath.c
index f7ad6d2a45d..fbb5de6922b 100644
--- a/src/common/relpath.c
+++ b/src/common/relpath.c
@@ -29,7 +29,7 @@
  * documentation for pg_relation_size(). Also keep FORKNAMECHARS above
  * up-to-date.
  */
-const char *forkNames[] = {
+const char *const forkNames[] = {
 	"main",						/* MAIN_FORKNUM */
 	"fsm",						/* FSM_FORKNUM */
 	"vm",						/* VISIBILITYMAP_FORKNUM */
diff --git a/src/include/common/relpath.h b/src/include/common/relpath.h
index 8795464a27a..23a226d058e 100644
--- a/src/include/common/relpath.h
+++ b/src/include/common/relpath.h
@@ -25,7 +25,8 @@
 #define TABLESPACE_VERSION_DIRECTORY	"PG_" PG_MAJORVERSION "_" \
 									CppAsString2(CATALOG_VERSION_NO)
 
-extern const char *forkNames[];
+extern const char *const forkNames[];
+
 extern int	forkname_chars(const char *str, ForkNumber *fork);
 extern char *relpathbackend(RelFileNode rnode, BackendId backend,
 			   ForkNumber forknum);
diff --git a/src/include/mb/pg_wchar.h b/src/include/mb/pg_wchar.h
index 74aacc4368f..6154d20969c 100644
--- a/src/include/mb/pg_wchar.h
+++ b/src/include/mb/pg_wchar.h
@@ -303,33 +303,23 @@ typedef enum pg_enc
 #define PG_VALID_FE_ENCODING(_enc)	PG_VALID_ENCODING(_enc)
 
 /*
- * Encoding names with all aliases
- */
-typedef struct pg_encname
-{
-	char	   *name;
-	pg_enc		encoding;
-} pg_encname;
-
-extern pg_encname pg_encname_tbl[];
-extern unsigned int pg_encname_tbl_sz;
-
-/*
- * Careful:
+ * Table for mapping an encoding number to official encoding name and
+ * possibly other subsidiary data.	Be careful to check encoding number
+ * before accessing a table entry!
  *
  * if (PG_VALID_ENCODING(encoding))
  *		pg_enc2name_tbl[ encoding ];
  */
 typedef struct pg_enc2name
 {
-	char	   *name;
+	const char *name;
 	pg_enc		encoding;
 #ifdef WIN32
 	unsigned	codepage;		/* codepage for WIN32 */
 #endif
 } pg_enc2name;
 
-extern pg_enc2name pg_enc2name_tbl[];
+extern const pg_enc2name pg_enc2name_tbl[];
 
 /*
  * Encoding names for gettext
@@ -340,7 +330,7 @@ typedef struct pg_enc2gettext
 	const char *name;
 } pg_enc2gettext;
 
-extern pg_enc2gettext pg_enc2gettext_tbl[];
+extern const pg_enc2gettext pg_enc2gettext_tbl[];
 
 /*
  * pg_wchar stuff
@@ -373,7 +363,7 @@ typedef struct
 	int			maxmblen;		/* max bytes for a char in this encoding */
 } pg_wchar_tbl;
 
-extern pg_wchar_tbl pg_wchar_table[];
+extern const pg_wchar_tbl pg_wchar_table[];
 
 /*
  * UTF-8 to local code conversion map
@@ -441,8 +431,6 @@ extern int	pg_valid_server_encoding_id(int encoding);
  * Remaining functions are not considered part of libpq's API, though many
  * of them do exist inside libpq.
  */
-extern pg_encname *pg_char_to_encname_struct(const char *name);
-
 extern int	pg_mb2wchar(const char *from, pg_wchar *to);
 extern int	pg_mb2wchar_with_len(const char *from, pg_wchar *to, int len);
 extern int pg_encoding_mb2wchar_with_len(int encoding,
diff --git a/src/include/utils/datetime.h b/src/include/utils/datetime.h
index b38d2514fe7..12f1e7753c7 100644
--- a/src/include/utils/datetime.h
+++ b/src/include/utils/datetime.h
@@ -247,6 +247,8 @@ do { \
  * Include check for leap year.
  */
 
+extern const char *const months[];		/* months (3-char abbreviations) */
+extern const char *const days[];	/* days (full names) */
 extern const int day_tab[2][13];
 
 #define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))