{"id":985,"date":"2008-11-10T10:38:00","date_gmt":"2008-11-10T10:38:00","guid":{"rendered":"\/blogs\/paul\/post\/Conference-Questions-Pot-Pourri-8-How-to-move-constraint-indexes.aspx"},"modified":"2008-11-10T10:38:00","modified_gmt":"2008-11-10T10:38:00","slug":"conference-questions-pot-pourri-8-how-to-move-constraint-indexes","status":"publish","type":"post","link":"https:\/\/www.sqlskills.com\/blogs\/paul\/conference-questions-pot-pourri-8-how-to-move-constraint-indexes\/","title":{"rendered":"Conference Questions Pot-Pourri #8: How to move constraint indexes?"},"content":{"rendered":"

\nIt's been a long time since the last Conference Questions Pot-Pourri – in fact it was at the last SQL Connections in Orlando in April. Now we're in Las Vegas doing SQL Connections Fall – Kimberly's lecturing for an hour on partitioning so I can get out a quick post. <\/font>\n<\/p>\n

\nThis is a question that came up yesterday – can CREATE INDEX … WITH DROP_EXISTING be used to move indexes that enforce constraints? Let's check it out. <\/font>\n<\/p>\n

\nFirst up I'm going to create a couple of tables. Table t1 has a unique constraint backed by a nonclustered index. Table t1 has a primary key constraint backed by a clustered index.<\/font>\n<\/p>\n

<\/p>\n

\n

\n\tCREATE DATABASE<\/font> ConstraintTest;<\/font>
\n\tGO
\n\tUSE<\/font> ConstraintTest;<\/font>
\n\tGO\n\t<\/p>\n

\n\tCREATE TABLE<\/font> UniqueConstraint (<\/font>c1 INT<\/font> UNIQUE NONCLUSTERED<\/font>);<\/font>
\n\tGO
\n\tINSERT INTO<\/font> UniqueConstraint VALUES<\/font> (<\/font>1);<\/font>
\n\tGO\n\t<\/p>\n

\n\tCREATE TABLE<\/font> PrimaryKeyConstraint (<\/font>c2 INT<\/font> PRIMARY KEY CLUSTERED<\/font>);<\/font>
\n\tGO
\n\tINSERT INTO<\/font> PrimaryKeyConstraint VALUES<\/font> (<\/font>1);<\/font>
\n\tGO\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\n(Oops – in the original post I c&p'd the wrong code and had the second table as a unique nonclustered constraint too – sorry for the mixup) <\/font>\n<\/p>\n

\nNow I'll add another filegroup that we'll try to move the indexes into.<\/font>\n<\/p>\n

<\/p>\n

\n

\n\tALTER DATABASE<\/font> ConstraintTest ADD FILEGROUP<\/font> ExtraFilegroup;<\/font>
\n\tGO\n\t<\/p>\n

\n\tALTER DATABASE<\/font> ConstraintTest ADD FILE<\/font> (<\/font>
\n\t   NAME<\/font> =<\/font> ExtraFile1,<\/font>
\n\t   FILENAME<\/font> =<\/font> 'C:\\SQLskills\\ExtraFile1.ndf'<\/font>,<\/font>
\n\t   SIZE<\/font> =<\/font> 5MB)<\/font>
\n\tTO FILEGROUP<\/font> ExtraFilegroup;<\/font>
\n\tGO\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\nNow I'll try moving the nonclustered index enforcing the unique constraint.<\/font>\n<\/p>\n

<\/p>\n

\n

\n\tSELECT<\/font> [name],<\/font> [index_id] FROM<\/font> sys.indexes<\/font>
\n\tWHERE<\/font> [object_id] =<\/font> OBJECT_ID<\/font> (<\/font>'UniqueConstraint'<\/font>)<\/font>
\n\tGO\n\t<\/p>\n

\n\tname                           index_id
\n\t—————————— ——–
\n\tNULL                           0
\n\tUQ__UniqueConstraint__7C8480AE 2\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\nThe index we want is index ID=2, so we should be able to move it as follows:<\/font>\n<\/p>\n

<\/p>\n

\n

\n\tCREATE UNIQUE NONCLUSTERED INDEX<\/font> UQ__UniqueConstraint__7C8480AE
\n\tON<\/font> UniqueConstraint (<\/font>c1)<\/font> WITH<\/font> (<\/font>DROP_EXISTING<\/font> =<\/font> ON<\/font>)<\/font>
\n\tON<\/font> ExtraFilegroup;<\/font>
\n\tGO\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\nNo problem! Now let's try the same thing for the clustered primary key constraint.<\/font> <\/font>\n<\/p>\n

<\/p>\n

\n

\n\tSELECT<\/font> [name],<\/font> [index_id] FROM<\/font> sys.indexes<\/font>
\n\tWHERE<\/font> [object_id] =<\/font> OBJECT_ID<\/font> (<\/font>'PrimaryKeyConstraint'<\/font>)<\/font>
\n\tGO\n\t<\/p>\n

\n\tname                           index_id
\n\t—————————— ——–
\n\tPK__PrimaryKeyConstr__7E6CC920 1\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\nWe only have one choice, so we should be able to rebuild it using:<\/font>\n<\/p>\n

<\/p>\n

\n

\n\tCREATE CLUSTERED INDEX<\/font> PK__PrimaryKeyConstr__7E6CC920
\n\tON<\/font> PrimaryKeyConstraint (<\/font>c2)<\/font> WITH<\/font> (<\/font>DROP_EXISTING<\/font> =<\/font> ON<\/font>)<\/font>
\n\tON<\/font> ExtraFilegroup;<\/font>
\n\tGO\n\t<\/p>\n

\n\tMsg 1907, Level 16, State 1, Line 1
\n\tCannot recreate index 'PK__PrimaryKeyConstr__7E6CC920'. The new index definition does not match the constraint being enforced by the existing index.<\/font>\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\nHmm – what am I missing? I'll check sys.indexes again and not filter the columns this time:<\/font>\n<\/p>\n

<\/p>\n

\n

\n\tSELECT<\/font> *<\/font> FROM<\/font> sys.indexes
\n\t<\/font>WHERE<\/font> [object_id] =<\/font> OBJECT_ID<\/font> (<\/font>'PrimaryKeyConstraint'<\/font>)<\/font>
\n\tGO\n\t<\/p>\n

\n\tobject_id  name                           index_id type type_desc is_unique
\n\t———- —————————— ——– —- ——— ———
\n\t2105058535 PK__PrimaryKeyConstr__7E6CC920 1        1    CLUSTERED 1\n\t<\/p>\n

\n\tdata_space_id ignore_dup_key is_primary_key is_unique_constraint fill_factor
\n\t————- ————– ————– ——————– ———–
\n\t1             0              1              0                    0<\/font>\n\t<\/p>\n

\n\tis_padded is_disabled is_hypothetical allow_row_locks allow_page_locks
\n\t——— ———– ————— ————— —————-
\n\t0<\/font>         0           0               1               1<\/font>\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\nAh – I was missing the unique attribute on the index. What I need to do is the following:<\/font>\n<\/p>\n

<\/p>\n

\n

\n\tCREATE UNIQUE CLUSTERED INDEX<\/font> PK__PrimaryKeyConstr__7E6CC920
\n\tON<\/font> PrimaryKeyConstraint (<\/font>c2)<\/font> WITH<\/font> (<\/font>DROP_EXISTING<\/font> =<\/font> ON<\/font>)<\/font>
\n\tON<\/font> ExtraFilegroup;<\/font>
\n\tGO\n\t<\/p>\n<\/blockquote>\n

<\/font><\/p>\n

\nAnd that works fine. So – the answer is yes, you can use CREATE INDEX … WITH DROP_EXISTING<\/font> to move indexes that enforce constraints. This is really good, as it allows you to move these indexes without having to do DROP INDEX<\/font> then CREATE INDEX<\/font>. That method is bad, as it creates a window of opportunity for someone to enter data that violates the constraint while the index is dropped.<\/font><\/p>\n","protected":false},"excerpt":{"rendered":"

It's been a long time since the last Conference Questions Pot-Pourri – in fact it was at the last SQL Connections in Orlando in April. Now we're in Las Vegas doing SQL Connections Fall – Kimberly's lecturing for an hour on partitioning so I can get out a quick post. This is a question that […]<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26,28,38,47],"tags":[],"class_list":["post-985","post","type-post","status-publish","format-standard","hentry","category-conference-questions-pot-pourri","category-constraints","category-example-scripts","category-indexes-from-every-angle"],"yoast_head":"\nConference Questions Pot-Pourri #8: How to move constraint indexes? - Paul S. Randal<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.sqlskills.com\/blogs\/paul\/conference-questions-pot-pourri-8-how-to-move-constraint-indexes\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Conference Questions Pot-Pourri #8: How to move constraint indexes? - Paul S. Randal\" \/>\n<meta property=\"og:description\" content=\"It's been a long time since the last Conference Questions Pot-Pourri – in fact it was at the last SQL Connections in Orlando in April. Now we're in Las Vegas doing SQL Connections Fall – Kimberly's lecturing for an hour on partitioning so I can get out a quick post. This is a question that […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.sqlskills.com\/blogs\/paul\/conference-questions-pot-pourri-8-how-to-move-constraint-indexes\/\" \/>\n<meta property=\"og:site_name\" content=\"Paul S. 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