Function exec_simple_query

src/backend/tcop/postgres.c:1651–2056

* exec_simple_query * * Execute a "simple Query" protocol message. */

 * Execute a "simple Query" protocol message.
 */
void
exec_simple_query(const char *query_string)
{
	CommandDest dest = whereToSendOutput;
	MemoryContext oldcontext;
	List	   *parsetree_list;
	ListCell   *parsetree_item;
	bool		save_log_statement_stats = log_statement_stats;
	bool		was_logged = false;
	bool		use_implicit_block;
	char		msec_str[32];

	SIMPLE_FAULT_INJECTOR("exec_simple_query_start");

	if (Gp_role != GP_ROLE_EXECUTE)
		increment_command_count();

	/*
	 * Report query to various monitoring facilities.
	 */
	debug_query_string = query_string;

	pgstat_report_activity(STATE_RUNNING, query_string);

	TRACE_POSTGRESQL_QUERY_START(query_string);

	/*
	 * We use save_log_statement_stats so ShowUsage doesn't report incorrect
	 * results because ResetUsage wasn't called.
	 */
	if (save_log_statement_stats)
		ResetUsage();

	/*
	 * Start up a transaction command.  All queries generated by the
	 * query_string will be in this same command block, *unless* we find a
	 * BEGIN/COMMIT/ABORT statement; we have to force a new xact command after
	 * one of those, else bad things will happen in xact.c. (Note that this
	 * will normally change current memory context.)
	 */
	start_xact_command();

	/*
	 * Zap any pre-existing unnamed statement.  (While not strictly necessary,
	 * it seems best to define simple-Query mode as if it used the unnamed
	 * statement and portal; this ensures we recover any storage used by prior
	 * unnamed operations.)
	 */
	drop_unnamed_stmt();

	/*
	 * Switch to appropriate context for constructing parsetrees.
	 */
	oldcontext = MemoryContextSwitchTo(MessageContext);

	/*
	 * Do basic parsing of the query or queries (this should be safe even if
	 * we are in aborted transaction state!)