Timothy Messier
f00af362dc
When applying the limit and order by, the where clause also needs to be
applied to yield the correct results. This can be seen with an example.
Assuming a data set where there are 100 sessions, with 10 sessions
belonging to a user with id `u_user1` and 90 sessions belonging to
`u_user2`. If the constructed query is like:
select *
from
(select public_id from session limit 10) s,
session_list ss
where
s.public_id = ss.public_id
and s.user_id = 'u_user1'
order by create_time asc;
The initial sub-query with the limit could return sessions only
belonging to `u_user2`, then it would apply the where clause and exclude
all of the rows.
Instead if the query is:
with
session_ids as (
select public_id
from sessions as s
where
s.user_id = 'u_user1'
order by create_time asc
limit 10
)
select *
from session_list
where
session_list.public_id in (select * from session_ids)
order by create_time asc;
The CTE applies the where clause ensuring that only sessions for
`u_user1` are used for the final select from the view.
Note that the CTE is use primarily for readability.
This also adds an index on `session (create_time)` to aide the query
planner in performing the order by.
424 lines
10 KiB
Go
424 lines
10 KiB
Go
package session
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import (
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"fmt"
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"strings"
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)
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const (
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activateStateCte = `
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insert into session_state
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with not_active as (
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select session_id, 'active' as state
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from
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session s,
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session_state ss
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where
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s.public_id = ss.session_id and
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ss.state = 'pending' and
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ss.session_id = @session_id and
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s.version = @version and
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s.public_id not in(select session_id from session_state where session_id = @session_id and state = 'active')
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)
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select * from not_active;
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`
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// updateSessionState checks that we don't already have a row for the new
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// state or it's not already terminated (final state) before inserting a new
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// state.
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updateSessionState = `
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insert into session_state(session_id, state)
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select
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@session_id, @status
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from
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session s
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where
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s.public_id = @session_id and
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s.public_id not in (
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select
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session_id
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from
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session_state
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where
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-- already in the updated state
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(
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session_id = @session_id and
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state = @status
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) or
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-- already terminated
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session_id in (
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select
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session_id
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from
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session_state
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where
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session_id = @session_id and
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state = 'terminated'
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)
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);
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`
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authorizeConnectionCte = `
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with connections_available as (
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select
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s.public_id
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from
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session s
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where
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s.public_id = @session_id and
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(s.connection_limit = -1 or
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s.connection_limit > (select count(*) from session_connection sc where sc.session_id = @session_id ))
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),
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unexpired_session as (
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select
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s.public_id
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from
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session s
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where
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s.public_id in (select * from connections_available) and
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s.expiration_time > now()
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),
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active_session as (
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select
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ss.session_id as session_id,
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@public_id as public_id,
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@worker_id as server_id
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from
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session_state ss
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where
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ss.session_id in (select * from unexpired_session) and
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ss.state = 'active' and
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ss.end_time is null
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)
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insert into session_connection (
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session_id,
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public_id,
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server_id
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)
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select * from active_session;
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`
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remainingConnectionsCte = `
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with
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session_connection_count(current_connection_count) as (
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select count(*)
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from
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session_connection sc
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where
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sc.session_id = @session_id
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),
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session_connection_limit(expiration_time, connection_limit) as (
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select
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s.expiration_time,
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s.connection_limit
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from
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session s
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where
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s.public_id = @session_id
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)
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select expiration_time, connection_limit, current_connection_count
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from
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session_connection_limit, session_connection_count;
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`
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sessionPublicIdList = `
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select public_id, scope_id, user_id from session
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%s
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;
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`
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sessionList = `
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with
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session_ids as (
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select public_id
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from session as s
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-- where clause is constructed
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%s
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-- order by clause is constructed
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%s
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-- limit is constructed
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%s
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)
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select *
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from session_list
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where
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session_list.public_id in (select * from session_ids)
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-- order by clause again since order from cte is not guaranteed to be preserved
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%s
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;
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`
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terminateSessionIfPossible = `
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-- is terminate_session_id in a canceling state
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with session_version as (
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select
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version
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from
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session
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where public_id = @public_id
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),
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canceling_session(session_id) as
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(
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select
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session_id
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from
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session_state ss
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where
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ss.session_id = @public_id and
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ss.state = 'canceling' and
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ss.end_time is null
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)
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update session us
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set version = version +1,
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termination_reason =
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case
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-- timed out sessions
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when now() > us.expiration_time then 'timed out'
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-- canceling sessions
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when us.public_id in(
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select
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session_id
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from
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canceling_session cs
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where
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us.public_id = cs.session_id
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) then 'canceled'
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-- default: session connection limit reached.
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else 'connection limit'
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end
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where
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-- limit update to just the terminating_session_id
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us.public_id = @public_id and
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us.version = (select * from session_version) and
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termination_reason is null and
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-- session expired or connection limit reached
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(
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-- expired sessions...
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now() > us.expiration_time or
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-- connection limit reached...
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(
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-- handle unlimited connections...
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connection_limit != -1 and
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(
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select count (*)
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from session_connection sc
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where
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sc.session_id = us.public_id
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) >= connection_limit
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) or
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-- canceled sessions
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us.public_id in (
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select
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session_id
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from
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canceling_session cs
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where
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us.public_id = cs.session_id
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)
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) and
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-- make sure there are no existing connections
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us.public_id not in (
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select
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session_id
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from
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session_connection
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where public_id in (
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select
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connection_id
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from
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session_connection_state
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where
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state != 'closed' and
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end_time is null
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)
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)
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`
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// termSessionUpdate is one stmt that terminates sessions for the following
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// reasons:
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// * sessions that are expired and all their connections are closed.
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// * sessions that are canceling and all their connections are closed
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// * sessions that have exhausted their connection limit and all their connections are closed.
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termSessionsUpdate = `
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with canceling_session(session_id) as
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(
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select
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session_id
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from
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session_state ss
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where
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ss.state = 'canceling' and
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ss.end_time is null
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)
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update session us
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set termination_reason =
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case
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-- timed out sessions
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when now() > us.expiration_time then 'timed out'
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-- canceling sessions
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when us.public_id in(
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select
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session_id
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from
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canceling_session cs
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where
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us.public_id = cs.session_id
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) then 'canceled'
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-- default: session connection limit reached.
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else 'connection limit'
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end
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where
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termination_reason is null and
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-- session expired or connection limit reached
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(
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-- expired sessions...
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now() > us.expiration_time or
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-- connection limit reached...
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(
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-- handle unlimited connections...
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connection_limit != -1 and
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(
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select count (*)
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from session_connection sc
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where
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sc.session_id = us.public_id
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) >= connection_limit
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) or
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-- canceled sessions
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us.public_id in (
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select
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session_id
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from
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canceling_session cs
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where
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us.public_id = cs.session_id
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)
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) and
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-- make sure there are no existing connections
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us.public_id not in (
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select
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session_id
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from
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session_connection
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where public_id in (
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select
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connection_id
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from
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session_connection_state
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where
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state != 'closed' and
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end_time is null
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)
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);
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`
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// closeConnectionsForDeadServersCte finds connections that are:
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//
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// * not closed
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// * belong to servers that have not reported in within an acceptable
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// threshold of time
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//
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// and marks them as closed.
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//
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// The query returns the set of servers that have had connections closed
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// along with their last update time and the number of connections closed on
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// each.
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closeConnectionsForDeadServersCte = `
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with
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dead_servers (server_id, last_update_time) as (
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select private_id, update_time
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from server
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where update_time < wt_sub_seconds_from_now(@grace_period_seconds)
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),
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closed_connections (connection_id, server_id) as (
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update session_connection
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set closed_reason = 'system error'
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where server_id in (select server_id from dead_servers)
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and closed_reason is null
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returning public_id, server_id
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)
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select closed_connections.server_id,
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dead_servers.last_update_time,
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count(closed_connections.connection_id) as number_connections_closed
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from closed_connections
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join dead_servers
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on closed_connections.server_id = dead_servers.server_id
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group by closed_connections.server_id, dead_servers.last_update_time
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order by closed_connections.server_id;
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`
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orphanedConnectionsCte = `
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-- Find connections that are not closed so we can reference those IDs
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with
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unclosed_connections as (
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select connection_id
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from session_connection_state
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where
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-- It's the current state
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end_time is null
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-- Current state isn't closed state
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and state in ('authorized', 'connected')
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-- It's not in limbo between when it moved into this state and when
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-- it started being reported by the worker, which is roughly every
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-- 2-3 seconds
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and start_time < wt_sub_seconds_from_now(@worker_state_delay_seconds)
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),
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connections_to_close as (
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select public_id
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from session_connection
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where
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-- Related to the worker that just reported to us
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server_id = @server_id
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-- Only unclosed ones
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and public_id in (select connection_id from unclosed_connections)
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-- These are connection IDs that just got reported to us by the given
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-- worker, so they should not be considered closed.
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%s
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)
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update session_connection
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set
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closed_reason = 'system error'
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where
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public_id in (select public_id from connections_to_close)
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returning public_id;
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`
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checkIfNotActive = `
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select session_id, state
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from session_state ss
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where
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(ss.state = 'canceling' or ss.state = 'terminated')
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and ss.end_time is null
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%s
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;
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`
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)
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const (
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sessionCredentialDynamicBatchInsertBase = `
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insert into session_credential_dynamic
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( session_id, library_id, credential_purpose )
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values
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`
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sessionCredentialDynamicBatchInsertValue = `
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(?, ?, ?)`
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sessionCredentialDynamicBatchInsertReturning = `
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returning session_id, library_id, credential_id, credential_purpose;
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`
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)
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func batchInsertsessionCredentialDynamic(creds []*DynamicCredential) (string, []interface{}, error) {
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if len(creds) <= 0 {
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return "", nil, fmt.Errorf("empty slice of DynamicCredential, cannot build query")
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}
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batchInsertParams := make([]string, 0, len(creds))
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batchInsertArgs := make([]interface{}, 0, len(creds)*3)
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for _, cred := range creds {
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batchInsertParams = append(batchInsertParams, sessionCredentialDynamicBatchInsertValue)
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batchInsertArgs = append(batchInsertArgs, []interface{}{cred.SessionId, cred.LibraryId, cred.CredentialPurpose}...)
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}
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q := sessionCredentialDynamicBatchInsertBase + strings.Join(batchInsertParams, ",") + sessionCredentialDynamicBatchInsertReturning
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return q, batchInsertArgs, nil
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}
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