"A prepared statement has a name and a CachedPlanSource. They are stored in a hash table. See StorePreparedStatement() function. If you grep for callers of StorePreparedStatement(), you'll see that there are two: one in processing an EXECUTE statement, and one in handling the Extended Query Protocol."
Thank you, the functions in the grep are the ones I was looking for. Patrick On Sun, Oct 4, 2020 at 11:32 PM Heikki Linnakangas <hlinn...@iki.fi> wrote: > On 02/10/2020 23:10, Patrick REED wrote: > > Hi, > > > > I am having a hard time pinning down which function creates a prepared > > statement. Say in some language I create a Prepared Statement and send > > it off. Before the first time I execute the prepared statement, which > > function is the one that 'creates' the prepared statement. In other > > words, which function stores it. I know that StorePreparedStatement will > > cache it, but is there anything else. > > > > e.g. > > In your favorite language: > > > > |String statement = "Insert into table_one values 10"; PreparedStatement > > insert = con.prepareStatement(statement); insert.execute() | > > > > The very first time, does it store this just in the plancache or does it > > do something different to 'know' it has stored a Prepared Statement, so > > next time it will invoke it. > > Most drivers use what the Extended Query Protocol. The client first > sends a Parse message that contains the SQL text. Next, it sends a Bind > message that contains the query parameters, and Execute to execute it. > The Bind+Execute steps can be repeated multiple times, with different > query parameters. The PREPARE and EXECUTE statements do essentially the > same thing. > > In the server code, there is the plan cache. The plan cache tracks when > a plan needs to be invalidated and the query replanned. The handle to an > entry in the plan cache is a CachedPlanSource, which contains the SQL > original and enough information to (re-)plan the query as needed. The > plan cache has entries for all the prepared statements, but also for > statements in PL/pgSQL functions, statements prepared with SPI_prepare() > etc. The plan cache doesn't know or care where the statements came from, > they are all treated the same. > > A prepared statement has a name and a CachedPlanSource. They are stored > in a hash table. See StorePreparedStatement() function. If you grep for > callers of StorePreparedStatement(), you'll see that there are two: one > in processing an EXECUTE statement, and one in handling the Extended > Query Protocol. > > - Heikki >
