It's logical a prepared statement is kept available as long as the prepared statement is not closed. preparedStatementCacheQueriesĪ prepared statement is automatically cached. It is my personal opinion this is not obvious. Instead, it waits for 4 client-side executions before a server-side prepared statement is created. When a prepared statement is defined and executed in Java, it doesn't create a server-side prepared statement. preparedStatementCacheQueries, default: 256.The following settings can found on the Postgres jdbc documentation website: The client also dictates how the server-side of this is handled. On the client/java side there are a few settings with default values that dictate how the client uses prepared statements. Also, mind this is not a solution for every case.
Details, Details, Detailsīut there are some details that need to be aligned to make this work predictably.
Once a prepared statement exists in Postgres, Postgres can choose a generic plan, which -if chosen- means the planning step in Postgres will be skipped, which is a further reduction of work, and thus a potential improvement in performance. Despite the difference between a client-side and server-side prepared statement, they do work closely together. A prepared statement in the database has the advantage that it can skip the parse phase, and execute the bind and execute phases only, meaning a reduction of work. Despite looking quite alike, this distinction is important, as you will see. This is known as a 'server-side prepared statement'. The above construction is known as a 'client-side prepared statement'.Ī separate advantage of a client-side prepared statement is that it can create a prepared statement in the database. The obvious advantage of a prepared statement is that the statement doesn't need to be created in java again, a new value can be bound, and executed. What Are the Advantages of a Prepared Statement? In order to execute prepared statement p again, all that needs to be done is 2 for a new value, and 3 to execute the prepared statement again. An example: PreparedStatement p = c.prepareStatement("select i from t where i = ?") Ģ: set ('bind') the first variable of p as 99. What Is a Prepared Statement?Ī prepared statement is a statement that is defined so that its variables can be set, and executed. This post is about Postgres JDBC ( PGJDBC) prepared statements, the setting prepareThreshold, and the performance implication of it.
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