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ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# Try various things to happen to a partition with an incomplete detach
#
Use annotations to reduce instability of isolation-test results. We've long contended with isolation test results that aren't entirely stable. Some test scripts insert long delays to try to force stable results, which is not terribly desirable; but other erratic failure modes remain, causing unrepeatable buildfarm failures. I've spent a fair amount of time trying to solve this by improving the server-side support code, without much success: that way is fundamentally unable to cope with diffs that stem from chance ordering of arrival of messages from different server processes. We can improve matters on the client side, however, by annotating the test scripts themselves to show the desired reporting order of events that might occur in different orders. This patch adds three types of annotations to deal with (a) test steps that might or might not complete their waits before the isolationtester can see them waiting; (b) test steps in different sessions that can legitimately complete in either order; and (c) NOTIFY messages that might arrive before or after the completion of a step in another session. We might need more annotation types later, but this seems to be enough to deal with the instabilities we've seen in the buildfarm. It also lets us get rid of all the long delays that were previously used, cutting more than a minute off the runtime of the isolation tests. Back-patch to all supported branches, because the buildfarm instabilities affect all the branches, and because it seems desirable to keep isolationtester's capabilities the same across all branches to simplify possible future back-patching of tests. Discussion: https://postgr.es/m/327948.1623725828@sss.pgh.pa.us
2021-06-23 03:43:12 +02:00
# Note: When using "s1cancel", mark the target step (the one to be canceled)
# as blocking "s1cancel". This ensures consistent reporting regardless of
# whether "s1cancel" finishes before or after the other step reports failure.
Use annotations to reduce instability of isolation-test results. We've long contended with isolation test results that aren't entirely stable. Some test scripts insert long delays to try to force stable results, which is not terribly desirable; but other erratic failure modes remain, causing unrepeatable buildfarm failures. I've spent a fair amount of time trying to solve this by improving the server-side support code, without much success: that way is fundamentally unable to cope with diffs that stem from chance ordering of arrival of messages from different server processes. We can improve matters on the client side, however, by annotating the test scripts themselves to show the desired reporting order of events that might occur in different orders. This patch adds three types of annotations to deal with (a) test steps that might or might not complete their waits before the isolationtester can see them waiting; (b) test steps in different sessions that can legitimately complete in either order; and (c) NOTIFY messages that might arrive before or after the completion of a step in another session. We might need more annotation types later, but this seems to be enough to deal with the instabilities we've seen in the buildfarm. It also lets us get rid of all the long delays that were previously used, cutting more than a minute off the runtime of the isolation tests. Back-patch to all supported branches, because the buildfarm instabilities affect all the branches, and because it seems desirable to keep isolationtester's capabilities the same across all branches to simplify possible future back-patching of tests. Discussion: https://postgr.es/m/327948.1623725828@sss.pgh.pa.us
2021-06-23 03:43:12 +02:00
# Also, ensure the step after "s1cancel" is also an s1 step (use "s1noop" if
# necessary). This ensures we won't move on to the next step until the cancel
# is complete.
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
setup
{
CREATE TABLE d3_listp (a int) PARTITION BY LIST(a);
CREATE TABLE d3_listp1 PARTITION OF d3_listp FOR VALUES IN (1);
CREATE TABLE d3_listp2 PARTITION OF d3_listp FOR VALUES IN (2);
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
CREATE TABLE d3_pid (pid int);
INSERT INTO d3_listp VALUES (1);
}
teardown {
DROP TABLE IF EXISTS d3_listp, d3_listp1, d3_listp2, d3_pid;
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
}
session s1
step s1b { BEGIN; }
step s1brr { BEGIN ISOLATION LEVEL REPEATABLE READ; }
step s1s { SELECT * FROM d3_listp; }
step s1spart { SELECT * FROM d3_listp1; }
step s1cancel { SELECT pg_cancel_backend(pid) FROM d3_pid; }
step s1noop { }
step s1c { COMMIT; }
step s1alter { ALTER TABLE d3_listp1 ALTER a DROP NOT NULL; }
step s1insert { INSERT INTO d3_listp VALUES (1); }
step s1insertpart { INSERT INTO d3_listp1 VALUES (1); }
step s1drop { DROP TABLE d3_listp; }
step s1droppart { DROP TABLE d3_listp1; }
step s1trunc { TRUNCATE TABLE d3_listp; }
step s1list { SELECT relname FROM pg_catalog.pg_class
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
WHERE relname LIKE 'd3_listp%' ORDER BY 1; }
step s1describe { SELECT 'd3_listp' AS root, * FROM pg_partition_tree('d3_listp')
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
UNION ALL SELECT 'd3_listp1', * FROM pg_partition_tree('d3_listp1'); }
session s2
step s2begin { BEGIN; }
step s2snitch { INSERT INTO d3_pid SELECT pg_backend_pid(); }
step s2detach { ALTER TABLE d3_listp DETACH PARTITION d3_listp1 CONCURRENTLY; }
step s2detach2 { ALTER TABLE d3_listp DETACH PARTITION d3_listp2 CONCURRENTLY; }
step s2detachfinal { ALTER TABLE d3_listp DETACH PARTITION d3_listp1 FINALIZE; }
step s2drop { DROP TABLE d3_listp1; }
step s2commit { COMMIT; }
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# Try various things while the partition is in "being detached" state, with
# no session waiting.
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1describe s1alter
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1insert s1c
permutation s2snitch s1brr s1s s2detach s1cancel(s2detach) s1insert s1c s1spart
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1insertpart
# Test partition descriptor caching
permutation s2snitch s1b s1s s2detach2 s1cancel(s2detach2) s1c s1brr s1insert s1s s1insert s1c
permutation s2snitch s1b s1s s2detach2 s1cancel(s2detach2) s1c s1brr s1s s1insert s1s s1c
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# "drop" here does both tables
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1drop s1list
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# "truncate" only does parent, not partition
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1trunc s1spart
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# If a partition pending detach exists, we cannot drop another one
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1noop s2detach2 s1c
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1noop s2detachfinal s1c s2detach2
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1droppart s2detach2
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# When a partition with incomplete detach is dropped, we grab lock on parent too.
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s2begin s2drop s1s s2commit
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# Partially detach, then select and try to complete the detach. Reading
# from partition blocks (AEL is required on partition); reading from parent
# does not block.
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1b s1spart s2detachfinal s1c
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1b s1s s2detachfinal s1c
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY Allow a partition be detached from its partitioned table without blocking concurrent queries, by running in two transactions and only requiring ShareUpdateExclusive in the partitioned table. Because it runs in two transactions, it cannot be used in a transaction block. This is the main reason to use dedicated syntax: so that users can choose to use the original mode if they need it. But also, it doesn't work when a default partition exists (because an exclusive lock would still need to be obtained on it, in order to change its partition constraint.) In case the second transaction is cancelled or a crash occurs, there's ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final steps. The main trick to make this work is the addition of column pg_inherits.inhdetachpending, initially false; can only be set true in the first part of this command. Once that is committed, concurrent transactions that use a PartitionDirectory will include or ignore partitions so marked: in optimizer they are ignored if the row is marked committed for the snapshot; in executor they are always included. As a result, and because of the way PartitionDirectory caches partition descriptors, queries that were planned before the detach will see the rows in the detached partition and queries that are planned after the detach, won't. A CHECK constraint is created that duplicates the partition constraint. This is probably not strictly necessary, and some users will prefer to remove it afterwards, but if the partition is re-attached to a partitioned table, the constraint needn't be rechecked. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reviewed-by: Amit Langote <amitlangote09@gmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 22:00:28 +01:00
# DETACH FINALIZE in a transaction block. No insert/select on the partition
# is allowed concurrently with that.
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s1b s1spart s2detachfinal s1c
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s2begin s2detachfinal s2commit
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s2begin s2detachfinal s1spart s2commit
permutation s2snitch s1b s1s s2detach s1cancel(s2detach) s1c s2begin s2detachfinal s1insertpart s2commit