Add a reference to the connection from prepared statements #107
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Ref: trilogy-libraries#105 To close a prepared statement you need to have access to the connection that created it. But in managed languages like Ruby, the obvious thing to do is to close the prepared statement when the associated object is garbage collected. But the order in which objects are garbaged collected is never guaranteed so when freeing a statement the connection might have been freed already and it's hard to detect. We checked how libmysqlclient handles it, and each `MYSQL_STMT` has a reference to its `MYSQL` (connection), and the connection keeps a doubly linked list of the statements it created. When a statement is closed it's removed from the list, when the connection is closed, all the connection references are set to NULL. We implemented exactly the same logic here. Additionally, prepared statement can only be used with the connection they were created from. As such having all the `trilogy_stmt_*` function take a connection isn't great for usability. So this change opens the door to only taking a `trilogy_stmt_t *`. Co-Authored-By: Adrianna Chang <adrianna.chang@shopify.com>
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Ref: #105
To close a prepared statement you need to have access to the connection that created it.
But in managed languages like Ruby, the obvious thing to do is to close the prepared statement when the associated object is garbage collected.
But the order in which objects are garbaged collected is never guaranteed so when freeing a statement the connection might have been freed already and it's hard to detect.
We checked how libmysqlclient handles it, and each
MYSQL_STMThas a reference to itsMYSQL(connection), and the connection keeps a doubly linked list of the statements it created.When a statement is closed it's removed from the list, when the connection is closed, all the connection references are set to NULL.
We implemented exactly the same logic here.
Additionally, prepared statement can only be used with the connection they were created from. As such having all the
trilogy_stmt_*function take a connection isn't great for usability. So this change opens the door to only taking atrilogy_stmt_t *.