Yes, there are negative effects from this:
If you script out a change blocked by this flag you get something like the script below (all i am turning the ID column in Contact into an autonumbered IDENTITY column, but the table has dependencies).
Note potential errors that can occur while the following is running:
- Even microsoft warns that this may cause data loss (that comment is auto-generated)!
- for a period of time, foreign keys are not enforced.
- if you manually run this in ssms and the ' EXEC('INSERT INTO ' fails, and you let the following statements run (which they do by default, as they are split by 'go') then you will insert 0 rows, then drop the old table.
- if this is a big table, the runtime of the insert can be large, and the transaction is holding a schema modification lock, so blocks many things.
--
BEGIN TRANSACTION
GO
ALTER TABLE raw.Contact
DROP CONSTRAINT fk_Contact_AddressType
GO
ALTER TABLE ref.ContactpointType SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
BEGIN TRANSACTION
GO
ALTER TABLE raw.Contact
DROP CONSTRAINT fk_contact_profile
GO
ALTER TABLE raw.Profile SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
BEGIN TRANSACTION
GO
CREATE TABLE raw.Tmp_Contact
(
ContactID int NOT NULL IDENTITY (1, 1),
ProfileID int NOT NULL,
AddressType char(2) NOT NULL,
ContactText varchar(250) NULL
) ON [PRIMARY]
GO
ALTER TABLE raw.Tmp_Contact SET (LOCK_ESCALATION = TABLE)
GO
SET IDENTITY_INSERT raw.Tmp_Contact ON
GO
IF EXISTS(SELECT * FROM raw.Contact)
EXEC('INSERT INTO raw.Tmp_Contact (ContactID, ProfileID, AddressType, ContactText)
SELECT ContactID, ProfileID, AddressType, ContactText FROM raw.Contact WITH (HOLDLOCK TABLOCKX)')
GO
SET IDENTITY_INSERT raw.Tmp_Contact OFF
GO
ALTER TABLE raw.PostalAddress
DROP CONSTRAINT fk_AddressProfile
GO
ALTER TABLE raw.MarketingFlag
DROP CONSTRAINT fk_marketingflag_contact
GO
ALTER TABLE raw.Phones
DROP CONSTRAINT fk_phones_contact
GO
DROP TABLE raw.Contact
GO
EXECUTE sp_rename N'raw.Tmp_Contact', N'Contact', 'OBJECT'
GO
ALTER TABLE raw.Contact ADD CONSTRAINT
Idx_Contact_1 PRIMARY KEY CLUSTERED
(
ProfileID,
ContactID
)
GO
ALTER TABLE raw.Contact ADD CONSTRAINT
Idx_Contact UNIQUE NONCLUSTERED
(
ProfileID,
ContactID
)
GO
CREATE NONCLUSTERED INDEX idx_Contact_0 ON raw.Contact
(
AddressType
)
GO
ALTER TABLE raw.Contact ADD CONSTRAINT
fk_contact_profile FOREIGN KEY
(
ProfileID
) REFERENCES raw.Profile
(
ProfileID
) ON UPDATE NO ACTION
ON DELETE NO ACTION
GO
ALTER TABLE raw.Contact ADD CONSTRAINT
fk_Contact_AddressType FOREIGN KEY
(
AddressType
) REFERENCES ref.ContactpointType
(
ContactPointTypeCode
) ON UPDATE NO ACTION
ON DELETE NO ACTION
GO
COMMIT
BEGIN TRANSACTION
GO
ALTER TABLE raw.Phones ADD CONSTRAINT
fk_phones_contact FOREIGN KEY
(
ProfileID,
PhoneID
) REFERENCES raw.Contact
(
ProfileID,
ContactID
) ON UPDATE NO ACTION
ON DELETE NO ACTION
GO
ALTER TABLE raw.Phones SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
BEGIN TRANSACTION
GO
ALTER TABLE raw.MarketingFlag ADD CONSTRAINT
fk_marketingflag_contact FOREIGN KEY
(
ProfileID,
ContactID
) REFERENCES raw.Contact
(
ProfileID,
ContactID
) ON UPDATE NO ACTION
ON DELETE NO ACTION
GO
ALTER TABLE raw.MarketingFlag SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
BEGIN TRANSACTION
GO
ALTER TABLE raw.PostalAddress ADD CONSTRAINT
fk_AddressProfile FOREIGN KEY
(
ProfileID,
AddressID
) REFERENCES raw.Contact
(
ProfileID,
ContactID
) ON UPDATE NO ACTION
ON DELETE NO ACTION
GO
ALTER TABLE raw.PostalAddress SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
...so do not answer with that!
