Function plpgsql_create_econtext

src/pl/plpgsql/src/pl_exec.c:8237–8298

* plpgsql_create_econtext --- create an eval_econtext for the current function * * We may need to create a new shared_simple_eval_estate too, if there's not * one already for the current transaction. The EState will be cleaned up at * transaction end. Ditto for shared_simple_eval_resowner. */

 * transaction end.  Ditto for shared_simple_eval_resowner.
 */
static void
plpgsql_create_econtext(PLpgSQL_execstate *estate)
{
	SimpleEcontextStackEntry *entry;

	/*
	 * Create an EState for evaluation of simple expressions, if there's not
	 * one already in the current transaction.  The EState is made a child of
	 * TopTransactionContext so it will have the right lifespan.
	 *
	 * Note that this path is never taken when beginning a DO block; the
	 * required EState was already made by plpgsql_inline_handler.  However,
	 * if the DO block executes COMMIT or ROLLBACK, then we'll come here and
	 * make a shared EState to use for the rest of the DO block.  That's OK;
	 * see the comments for shared_simple_eval_estate.  (Note also that a DO
	 * block will continue to use its private cast hash table for the rest of
	 * the block.  That's okay for now, but it might cause problems someday.)
	 */
	if (estate->simple_eval_estate == NULL)
	{
		MemoryContext oldcontext;

		if (shared_simple_eval_estate == NULL)
		{
			oldcontext = MemoryContextSwitchTo(TopTransactionContext);
			shared_simple_eval_estate = CreateExecutorState();
			MemoryContextSwitchTo(oldcontext);
		}
		estate->simple_eval_estate = shared_simple_eval_estate;
	}

	/*
	 * Likewise for the simple-expression resource owner.
	 */
	if (estate->simple_eval_resowner == NULL)
	{
		if (shared_simple_eval_resowner == NULL)
			shared_simple_eval_resowner =
				ResourceOwnerCreate(TopTransactionResourceOwner,
									"PL/pgSQL simple expressions");
		estate->simple_eval_resowner = shared_simple_eval_resowner;
	}

	/*
	 * Create a child econtext for the current function.
	 */
	estate->eval_econtext = CreateExprContext(estate->simple_eval_estate);

	/*
	 * Make a stack entry so we can clean up the econtext at subxact end.
	 * Stack entries are kept in TopTransactionContext for simplicity.
	 */
	entry = (SimpleEcontextStackEntry *)
		MemoryContextAlloc(TopTransactionContext,
						   sizeof(SimpleEcontextStackEntry));

	entry->stack_econtext = estate->eval_econtext;
	entry->xact_subxid = GetCurrentSubTransactionId();