DefineCollation() code cleanup

Reorganize the code in DefineCollation() so that the parts using the
FROM clause and the parts not doing so are more cleanly separated.  No
functionality change intended.

Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Discussion: https://www.postgresql.org/message-id/29ae752f-80e9-8d31-601c-62cf01cc93d8@enterprisedb.com

src/backend/commands/collationcmds.c

@@ -63,12 +63,11 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 	DefElem    *providerEl = NULL;
 	DefElem    *deterministicEl = NULL;
 	DefElem    *versionEl = NULL;
-	char	   *collcollate = NULL;
-	char	   *collctype = NULL;
-	char	   *collproviderstr = NULL;
-	bool		collisdeterministic = true;
-	int			collencoding = 0;
-	char		collprovider = 0;
+	char	   *collcollate;
+	char	   *collctype;
+	bool		collisdeterministic;
+	int			collencoding;
+	char		collprovider;
 	char	   *collversion = NULL;
 	Oid			newoid;
 	ObjectAddress address;
@@ -167,65 +166,71 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
 					 errmsg("collation \"default\" cannot be copied")));
 	}
-
-	if (localeEl)
+	else
 	{
-		collcollate = defGetString(localeEl);
-		collctype = defGetString(localeEl);
-	}
+		char	   *collproviderstr = NULL;
 
-	if (lccollateEl)
-		collcollate = defGetString(lccollateEl);
+		collcollate = NULL;
+		collctype = NULL;
 
-	if (lcctypeEl)
-		collctype = defGetString(lcctypeEl);
+		if (localeEl)
+		{
+			collcollate = defGetString(localeEl);
+			collctype = defGetString(localeEl);
+		}
 
-	if (providerEl)
-		collproviderstr = defGetString(providerEl);
+		if (lccollateEl)
+			collcollate = defGetString(lccollateEl);
 
-	if (deterministicEl)
-		collisdeterministic = defGetBoolean(deterministicEl);
+		if (lcctypeEl)
+			collctype = defGetString(lcctypeEl);
 
-	if (versionEl)
-		collversion = defGetString(versionEl);
+		if (providerEl)
+			collproviderstr = defGetString(providerEl);
 
-	if (collproviderstr)
-	{
-		if (pg_strcasecmp(collproviderstr, "icu") == 0)
-			collprovider = COLLPROVIDER_ICU;
-		else if (pg_strcasecmp(collproviderstr, "libc") == 0)
-			collprovider = COLLPROVIDER_LIBC;
+		if (deterministicEl)
+			collisdeterministic = defGetBoolean(deterministicEl);
+		else
+			collisdeterministic = true;
+
+		if (versionEl)
+			collversion = defGetString(versionEl);
+
+		if (collproviderstr)
+		{
+			if (pg_strcasecmp(collproviderstr, "icu") == 0)
+				collprovider = COLLPROVIDER_ICU;
+			else if (pg_strcasecmp(collproviderstr, "libc") == 0)
+				collprovider = COLLPROVIDER_LIBC;
+			else
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+						 errmsg("unrecognized collation provider: %s",
+								collproviderstr)));
+		}
 		else
+			collprovider = COLLPROVIDER_LIBC;
+
+		if (!collcollate)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
-					 errmsg("unrecognized collation provider: %s",
-							collproviderstr)));
-	}
-	else if (!fromEl)
-		collprovider = COLLPROVIDER_LIBC;
-
-	if (!collcollate)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
-				 errmsg("parameter \"lc_collate\" must be specified")));
+					 errmsg("parameter \"lc_collate\" must be specified")));
 
-	if (!collctype)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
-				 errmsg("parameter \"lc_ctype\" must be specified")));
+		if (!collctype)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("parameter \"lc_ctype\" must be specified")));
 
-	/*
-	 * Nondeterministic collations are currently only supported with ICU
-	 * because that's the only case where it can actually make a difference.
-	 * So we can save writing the code for the other providers.
-	 */
-	if (!collisdeterministic && collprovider != COLLPROVIDER_ICU)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("nondeterministic collations not supported with this provider")));
+		/*
+		 * Nondeterministic collations are currently only supported with ICU
+		 * because that's the only case where it can actually make a difference.
+		 * So we can save writing the code for the other providers.
+		 */
+		if (!collisdeterministic && collprovider != COLLPROVIDER_ICU)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("nondeterministic collations not supported with this provider")));
 
-	if (!fromEl)
-	{
 		if (collprovider == COLLPROVIDER_ICU)
 		{
 #ifdef USE_ICU