shard-crystal-db/src/db/pool_prepared_statement.cr
2023-04-24 12:26:25 +02:00

69 lines
2.1 KiB
Crystal

module DB
# Represents a statement to be executed in any of the connections
# of the pool. The statement is not be executed in a prepared fashion.
# The execution of the statement is retried according to the pool configuration.
#
# See `PoolStatement`
class PoolPreparedStatement < PoolStatement
# connections where the statement was prepared
@connections = Set(WeakRef(Connection)).new
@mutex = Mutex.new
def initialize(db : Database, query : String)
super
# Prepares a statement on some connection
# otherwise the preparation is delayed until the first execution.
# After the first initialization the connection must be released
# it will be checked out when executing it.
statement_with_retry &.release_connection
# TODO use a round-robin selection in the pool so multiple sequentially
# initialized statements are assigned to different connections.
end
protected def do_close
@mutex.synchronize do
# TODO close all statements on all connections.
# currently statements are closed when the connection is closed.
# WHAT-IF the connection is busy? Should each statement be able to
# deallocate itself when the connection is free.
@connections.clear
end
end
# builds a statement over a real connection
# the connection is registered in `@connections`
private def build_statement : Statement
clean_connections
conn, existing = @mutex.synchronize do
@db.checkout_some(@connections)
end
begin
stmt = conn.prepared.build(@query)
rescue ex
conn.release
raise ex
end
unless existing
@mutex.synchronize do
@connections << WeakRef.new(conn)
end
end
stmt
end
private def clean_connections
@mutex.synchronize do
# remove disposed or closed connections
@connections.each do |ref|
conn = ref.value
if !conn || conn.closed?
@connections.delete ref
end
end
end
end
end
end