Give orderToAuthz2 an auto-increment ID column (#6835)

Replace the current orderToAuthz2 table schema with one that includes an
auto-increment ID column, so that this table can be partitioned simply
by ID, like all of our other partitioned tables.

Update the SA so that when it selects from a join over this table and
the authz2 table, it explicitly selects the columns from the authz2
table, to avoid the ambiguity introduced by having two columns named
"id" in the result set.

This work is already in-progress in prod, represented by IN-8916 and
IN-8928.

Fixes https://github.com/letsencrypt/boulder/issues/6820

sa/db-next/boulder_sa/20230419000003_OrderToAuthzID.sql

@@ -0,0 +1,27 @@
+-- +migrate Up
+-- SQL in section 'Up' is executed when this migration is applied
+
+DROP TABLE orderToAuthz2;
+CREATE TABLE `orderToAuthz2` (
+  `id` bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+  `orderID` bigint(20) UNSIGNED NOT NULL,
+  `authzID` bigint(20) UNSIGNED NOT NULL,
+  PRIMARY KEY (`id`),
+  KEY `orderID_idx` (`orderID`),
+  KEY `authzID_idx` (`authzID`)
+) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4
+ PARTITION BY RANGE (`id`)
+(PARTITION p_start VALUES LESS THAN (MAXVALUE));
+
+-- +migrate Down
+-- SQL section 'Down' is executed when this migration is rolled back
+
+DROP TABLE orderToAuthz2;
+CREATE TABLE `orderToAuthz2` (
+  `orderID` bigint(20) NOT NULL,
+  `authzID` bigint(20) NOT NULL,
+  PRIMARY KEY (`orderID`,`authzID`),
+  KEY `authzID` (`authzID`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
+ PARTITION BY RANGE COLUMNS(orderID, authzID)
+(PARTITION p_start VALUES LESS THAN (MAXVALUE, MAXVALUE));

sa/saro.go

@@ -994,6 +994,16 @@ func (ssa *SQLStorageAuthorityRO) GetValidOrderAuthorizations2(ctx context.Conte
 		return nil, errIncompleteRequest
 	}
 
+	// The authz2 and orderToAuthz2 tables both have a column named "id", so we
+	// need to be explicit about which table's "id" column we want to select.
+	qualifiedAuthzFields := strings.Split(authzFields, " ")
+	for i, field := range qualifiedAuthzFields {
+		if field == "id," {
+			qualifiedAuthzFields[i] = "authz2.id,"
+			break
+		}
+	}
+
 	var ams []authzModel
 	_, err := ssa.dbReadOnlyMap.WithContext(ctx).Select(
 		&ams,
@@ -1003,7 +1013,7 @@ func (ssa *SQLStorageAuthorityRO) GetValidOrderAuthorizations2(ctx context.Conte
 			authz2.expires > :expires AND
 			authz2.status = :status AND
 			orderToAuthz2.orderID = :orderID`,
-			authzFields,
+			strings.Join(qualifiedAuthzFields, " "),
 		),
 		map[string]interface{}{
 			"regID":   req.AcctID,