Fix implicitly used collations after ALTER DOMAIN (#8434)

* Fix implicitly used collations after ALTER DOMAIN

* Correction for COLLATE used together with the domain name

* Ensure ALTER DOMAIN preserves the specified collation, it also fixes #1627: ALTER DOMAIN supporting collation change

Author: dyemanov

src/dsql/DdlNodes.epp

@@ -6480,11 +6480,10 @@ void RelationNode::defineField(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch
 			storeGlobalField(tdbb, transaction, fieldDefinition.fieldSource, field,
 				computedSource, computedValue);
 		}
-		else
+		else if (field->collate.hasData())
 		{
 			// Resolve possible additional collation for domains. For plain types it is already resolved above.
-			if (field->collate.hasData())
-				DDL_resolve_intl_type(dsqlScratch, field, field->collate);
+			DDL_resolve_intl_type(dsqlScratch, field, field->collate);
 		}
 
 		if ((relation->rel_flags & REL_external) &&
@@ -6541,7 +6540,8 @@ void RelationNode::defineField(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch
 		}
 
 		fieldDefinition.defaultValue = defaultValue;
-		fieldDefinition.collationId = field->collationId;
+		if (field->typeOfName.isEmpty() || field->collate.hasData())
+			fieldDefinition.collationId = field->collationId;
 		fieldDefinition.store(tdbb, transaction);
 
 		// Define the field constraints.

src/dsql/parse.y

@@ -4281,13 +4281,7 @@ alter_domain_op($alterDomainNode)
 	| TO symbol_column_name
 		{ setClause($alterDomainNode->renameTo, "DOMAIN NAME", *$2); }
 	| TYPE non_array_type
-		{
-			//// FIXME: ALTER DOMAIN doesn't support collations, and altered domain's
-			//// collation is always lost.
-			dsql_fld* type = $2;
-			type->collate = "";
-			setClause($alterDomainNode->type, "DOMAIN TYPE", type);
-		}
+		{ setClause($alterDomainNode->type, "DOMAIN TYPE", $2);}
 	;
 
 %type alter_ops(<relationNode>)