Add a hack to make migration deadlocks less likely in some common cases #6379
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This is a partial mitigation of #6304. There are a lot of opportunities for deadlocks between DDL (which can take a lot of full locks on things) and long-running queries. One place this comes up is with views, since recreating a view requires a lock. When adding things to tables, our DDL must modify the table, then modify the view. This poses a deadlock risk with queries, which nearly always will access the view before accessing the table (since the table is how they get to the view). Put a hacky and hopefully temporary bandage around this particular deadlock case by injecting a no-op ALTER VIEW before the first ALTER of some table. This ensures that DDL locks the inhview before the real table, making the lock order match the typical query lock order.
elprans
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Oct 27, 2023
msullivan
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Oct 28, 2023
…es (#6379) This is a partial mitigation of #6304. There are a lot of opportunities for deadlocks between DDL (which can take a lot of full locks on things) and long-running queries. One place this comes up is with views, since recreating a view requires a lock. When adding things to tables, our DDL must modify the table, then modify the view. This poses a deadlock risk with queries, which nearly always will access the view before accessing the table (since the table is how they get to the view). Put a hacky and hopefully temporary bandage around this particular deadlock case by injecting a no-op ALTER VIEW before the first ALTER of some table. This ensures that DDL locks the inhview before the real table, making the lock order match the typical query lock order.
aljazerzen
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Oct 30, 2023
…es (#6379) This is a partial mitigation of #6304. There are a lot of opportunities for deadlocks between DDL (which can take a lot of full locks on things) and long-running queries. One place this comes up is with views, since recreating a view requires a lock. When adding things to tables, our DDL must modify the table, then modify the view. This poses a deadlock risk with queries, which nearly always will access the view before accessing the table (since the table is how they get to the view). Put a hacky and hopefully temporary bandage around this particular deadlock case by injecting a no-op ALTER VIEW before the first ALTER of some table. This ensures that DDL locks the inhview before the real table, making the lock order match the typical query lock order.
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This is a partial mitigation of #6304.
There are a lot of opportunities for deadlocks between DDL
(which can take a lot of full locks on things) and
long-running queries. One place this comes up is with views,
since recreating a view requires a lock. When adding things to
tables, our DDL must modify the table, then modify the view.
This poses a deadlock risk with queries, which nearly always
will access the view before accessing the table (since the table
is how they get to the view).
Put a hacky and hopefully temporary bandage around this particular
deadlock case by injecting a no-op ALTER VIEW before the first
ALTER of some table. This ensures that DDL locks the inhview
before the real table, making the lock order match the typical
query lock order.