ALTER CONSTRAINT clause for NOT NULL constraints

Author: aafemt

doc/sql.extensions/README.ddl.txt

@@ -673,7 +673,7 @@ Syntax:
 
 ALTER TABLE ALTER CONSTRAINT <constraint name> [NOT] ENFORCED
 
-Supported for UNIQUE, PRIMARY KEY, FOREIGN KEY and CHECK constraints.
+Supported for UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK AND NOT NULL constraints.
 Primary and unique keys cannot be deactivated if they are referenced by any active foreign key.
 
 The corresponding ALTER INDEX and ALTER TRIGGER statements are allowed as well.

src/dsql/DdlNodes.epp

@@ -7965,17 +7965,70 @@ void AlterRelationNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScratc
 
 							FOR (REQUEST_HANDLE requestHandle TRANSACTION_HANDLE transaction)
 								TRG IN RDB$TRIGGERS CROSS
-								CHK IN RDB$CHECK_CONSTRAINTS WITH
-								TRG.RDB$RELATION_NAME EQ name.c_str() AND
-								TRG.RDB$TRIGGER_NAME EQ CHK.RDB$TRIGGER_NAME AND
-								CHK.RDB$CONSTRAINT_NAME EQ clause->name.c_str()
+								CHK IN RDB$CHECK_CONSTRAINTS
+								WITH TRG.RDB$RELATION_NAME EQ name.c_str() AND
+									 TRG.RDB$TRIGGER_NAME EQ CHK.RDB$TRIGGER_NAME AND
+									 CHK.RDB$CONSTRAINT_NAME EQ clause->name.c_str()
 							{
 								MODIFY TRG
 									TRG.RDB$TRIGGER_INACTIVE = clause->enforced ? FALSE : TRUE;
 								END_MODIFY
 							}
 							END_FOR
 						}
+						else if (strcmp(RC.RDB$CONSTRAINT_TYPE, NOT_NULL_CNSTRT) == 0)
+						{
+							AutoRequest requestHandle;
+
+							FOR (REQUEST_HANDLE requestHandle TRANSACTION_HANDLE transaction)
+								CHK IN RDB$CHECK_CONSTRAINTS CROSS
+								RF  IN RDB$RELATION_FIELDS
+								WITH CHK.RDB$CONSTRAINT_NAME EQ clause->name.c_str() AND
+									 CHK.RDB$TRIGGER_NAME EQ RF.RDB$FIELD_NAME AND
+									 RF.RDB$RELATION_NAME EQ name.c_str()
+							{
+								// Identity column cannot be NULL-able.
+								if (RF.RDB$IDENTITY_TYPE.NULL == FALSE)
+								{
+									fb_utils::exact_name(RF.RDB$FIELD_NAME);
+									// msg 274: Identity column @1 of table @2 cannot be changed to NULLable
+									status_exception::raise(Arg::PrivateDyn(274) << RF.RDB$FIELD_NAME << name.c_str());
+								}
+
+								// Column of an active primary key cannot be nullable
+								AutoRequest request3;
+
+								FOR (REQUEST_HANDLE request3 TRANSACTION_HANDLE transaction)
+									ISG IN RDB$INDEX_SEGMENTS CROSS
+									IDX IN RDB$INDICES CROSS
+									RC2 IN RDB$RELATION_CONSTRAINTS
+									WITH ISG.RDB$FIELD_NAME EQ RF.RDB$FIELD_NAME AND
+										 ISG.RDB$INDEX_NAME EQ IDX.RDB$INDEX_NAME AND
+										 IDX.RDB$RELATION_NAME EQ name.c_str() AND
+										 (IDX.RDB$INDEX_INACTIVE EQ 0 OR IDX.RDB$INDEX_INACTIVE MISSING) AND
+										 RC2.RDB$INDEX_NAME EQ IDX.RDB$INDEX_NAME AND
+										 RC2.RDB$CONSTRAINT_TYPE EQ PRIMARY_KEY
+								{
+									status_exception::raise(Arg::Gds(isc_primary_key_notnull));
+								}
+								END_FOR
+
+								// Otherwise it is fine
+								MODIFY RF
+									if (clause->enforced)
+									{
+										RF.RDB$NULL_FLAG.NULL = FALSE;
+										RF.RDB$NULL_FLAG = TRUE;
+									}
+									else
+									{
+										RF.RDB$NULL_FLAG.NULL = TRUE;
+										RF.RDB$NULL_FLAG = FALSE; // For symmetry
+									}
+								END_MODIFY
+							}
+							END_FOR
+						}
 						else
 							status_exception::raise(Arg::Gds(isc_wish_list) << Arg::Gds(isc_ref_cnstrnt_update));
 					}

src/isql/show.epp

@@ -6281,17 +6281,26 @@ static processing_state show_table(const SCHAR* relation_name, bool isView)
 	END_ERROR
 
 	FOR R_C IN RDB$RELATION_CONSTRAINTS CROSS
-		C_C IN RDB$CHECK_CONSTRAINTS
+		C_C IN RDB$CHECK_CONSTRAINTS CROSS
+		R_F IN RDB$RELATION_FIELDS
 		WITH R_C.RDB$RELATION_NAME   EQ relation_name
 		AND R_C.RDB$CONSTRAINT_TYPE EQ 'NOT NULL'
 		AND R_C.RDB$CONSTRAINT_NAME EQ C_C.RDB$CONSTRAINT_NAME
+		AND R_F.RDB$FIELD_NAME EQ C_C.RDB$TRIGGER_NAME
+		AND R_F.RDB$RELATION_NAME EQ R_C.RDB$RELATION_NAME
 
 		if (!fb_utils::implicit_integrity(R_C.RDB$CONSTRAINT_NAME))
 		{
 			fb_utils::exact_name(C_C.RDB$TRIGGER_NAME);
 			fb_utils::exact_name(R_C.RDB$CONSTRAINT_NAME);
 			isqlGlob.printf("CONSTRAINT %s:%s", R_C.RDB$CONSTRAINT_NAME, NEWLINE);
-			isqlGlob.printf("  Not Null Column (%s)%s", C_C.RDB$TRIGGER_NAME, NEWLINE);
+			isqlGlob.printf("  Not Null Column (%s)", C_C.RDB$TRIGGER_NAME);
+			if (R_F.RDB$NULL_FLAG.NULL == TRUE || R_F.RDB$NULL_FLAG == FALSE)
+			{
+				// Despite of constraint existence this field allows NULLs
+				isqlGlob.printf(" Not enforced");
+			}
+			isqlGlob.printf("%s", NEWLINE);
 		}
 	END_FOR
 	ON_ERROR