postgres.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 2,551 行 · 第 1/5 页

 */
List *
pg_rewrite_queries(List *querytree_list)
{
	List	   *new_list = NIL;
	List	   *list_item;

	if (log_parser_stats)
		ResetUsage();

	/*
	 * rewritten queries are collected in new_list.  Note there may be
	 * more or fewer than in the original list.
	 */
	foreach(list_item, querytree_list)
	{
		Query	   *querytree = (Query *) lfirst(list_item);

		if (Debug_print_parse)
			elog_node_display(DEBUG1, "parse tree", querytree,
							  Debug_pretty_print);

		if (querytree->commandType == CMD_UTILITY)
		{
			/* don't rewrite utilities, just dump 'em into new_list */
			new_list = lappend(new_list, querytree);
		}
		else
		{
			/* rewrite regular queries */
			List	   *rewritten = QueryRewrite(querytree);

			new_list = nconc(new_list, rewritten);
		}
	}

	querytree_list = new_list;

	if (log_parser_stats)
		ShowUsage("REWRITER STATISTICS");

#ifdef COPY_PARSE_PLAN_TREES

	/*
	 * Optional debugging check: pass querytree output through
	 * copyObject()
	 */
	new_list = (List *) copyObject(querytree_list);
	/* This checks both copyObject() and the equal() routines... */
	if (!equal(new_list, querytree_list))
		elog(WARNING, "copyObject() failed to produce an equal parse tree");
	else
		querytree_list = new_list;
#endif

	if (Debug_print_rewritten)
		elog_node_display(DEBUG1, "rewritten parse tree", querytree_list,
						  Debug_pretty_print);

	return querytree_list;
}


/* Generate a plan for a single already-rewritten query. */
Plan *
pg_plan_query(Query *querytree)
{
	Plan	   *plan;

	/* Utility commands have no plans. */
	if (querytree->commandType == CMD_UTILITY)
		return NULL;

	if (log_planner_stats)
		ResetUsage();

	/* call the optimizer */
	plan = planner(querytree, false, 0);

	if (log_planner_stats)
		ShowUsage("PLANNER STATISTICS");

#ifdef COPY_PARSE_PLAN_TREES
	/* Optional debugging check: pass plan output through copyObject() */
	{
		Plan	   *new_plan = (Plan *) copyObject(plan);

		/*
		 * equal() currently does not have routines to compare Plan nodes,
		 * so don't try to test equality here.  Perhaps fix someday?
		 */
#ifdef NOT_USED
		/* This checks both copyObject() and the equal() routines... */
		if (!equal(new_plan, plan))
			elog(WARNING, "copyObject() failed to produce an equal plan tree");
		else
#endif
			plan = new_plan;
	}
#endif

	/*
	 * Print plan if debugging.
	 */
	if (Debug_print_plan)
		elog_node_display(DEBUG1, "plan", plan, Debug_pretty_print);

	return plan;
}

/*
 * Generate plans for a list of already-rewritten queries.
 *
 * If needSnapshot is TRUE, we haven't yet set a snapshot for the current
 * query.  A snapshot must be set before invoking the planner, since it
 * might try to evaluate user-defined functions.  But we must not set a
 * snapshot if the list contains only utility statements, because some
 * utility statements depend on not having frozen the snapshot yet.
 * (We assume that such statements cannot appear together with plannable
 * statements in the rewriter's output.)
 */
List *
pg_plan_queries(List *querytrees, bool needSnapshot)
{
	List	   *plan_list = NIL;
	List	   *query_list;

	foreach(query_list, querytrees)
	{
		Query	   *query = (Query *) lfirst(query_list);
		Plan	   *plan;

		if (query->commandType == CMD_UTILITY)
		{
			/* Utility commands have no plans. */
			plan = NULL;
		}
		else
		{
			if (needSnapshot)
			{
				SetQuerySnapshot();
				needSnapshot = false;
			}
			plan = pg_plan_query(query);
		}

		plan_list = lappend(plan_list, plan);
	}

	return plan_list;
}


/*
 * exec_simple_query
 *
 * Execute a "simple Query" protocol message.
 */
static void
exec_simple_query(const char *query_string)
{
	CommandDest dest = whereToSendOutput;
	MemoryContext oldcontext;
	List	   *parsetree_list,
			   *parsetree_item;
	struct timeval start_t,
				stop_t;
	bool		save_log_duration = log_duration;
	int			save_log_min_duration_statement = log_min_duration_statement;
	bool		save_log_statement_stats = log_statement_stats;

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

	pgstat_report_activity(query_string);

	/*
	 * We use save_log_* so "SET log_duration = true"  and "SET
	 * log_min_duration_statement = true" don't report incorrect time
	 * because gettimeofday() wasn't called. Similarly,
	 * log_statement_stats has to be captured once.
	 */
	if (save_log_duration || save_log_min_duration_statement != -1)
		gettimeofday(&start_t, NULL);

	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.)
	 */
	unnamed_stmt_pstmt = NULL;
	if (unnamed_stmt_context)
	{
		DropDependentPortals(unnamed_stmt_context);
		MemoryContextDelete(unnamed_stmt_context);
	}
	unnamed_stmt_context = NULL;

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

	QueryContext = CurrentMemoryContext;

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

	/*
	 * Switch back to transaction context to enter the loop.
	 */
	MemoryContextSwitchTo(oldcontext);

	/*
	 * Run through the raw parsetree(s) and process each one.
	 */
	foreach(parsetree_item, parsetree_list)
	{
		Node	   *parsetree = (Node *) lfirst(parsetree_item);
		const char *commandTag;
		char		completionTag[COMPLETION_TAG_BUFSIZE];
		List	   *querytree_list,
				   *plantree_list;
		Portal		portal;
		DestReceiver *receiver;
		int16		format;

		/*
		 * Get the command name for use in status display (it also becomes
		 * the default completion tag, down inside PortalRun).	Set
		 * ps_status and do any special start-of-SQL-command processing
		 * needed by the destination.
		 */
		commandTag = CreateCommandTag(parsetree);

		set_ps_display(commandTag);

		BeginCommand(commandTag, dest);

		/*
		 * If we are in an aborted transaction, reject all commands except
		 * COMMIT/ABORT.  It is important that this test occur before we
		 * try to do parse analysis, rewrite, or planning, since all those
		 * phases try to do database accesses, which may fail in abort
		 * state. (It might be safe to allow some additional utility
		 * commands in this state, but not many...)
		 */
		if (IsAbortedTransactionBlockState())
		{
			bool		allowit = false;

			if (IsA(parsetree, TransactionStmt))
			{
				TransactionStmt *stmt = (TransactionStmt *) parsetree;

				if (stmt->kind == TRANS_STMT_COMMIT ||
					stmt->kind == TRANS_STMT_ROLLBACK)
					allowit = true;
			}

			if (!allowit)
				ereport(ERROR,
						(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
						 errmsg("current transaction is aborted, "
					 "commands ignored until end of transaction block")));
		}

		/* Make sure we are in a transaction command */
		start_xact_command();

		/* If we got a cancel signal in parsing or prior command, quit */
		CHECK_FOR_INTERRUPTS();

		/*
		 * OK to analyze, rewrite, and plan this query.
		 *
		 * Switch to appropriate context for constructing querytrees (again,
		 * these must outlive the execution context).
		 */
		oldcontext = MemoryContextSwitchTo(MessageContext);

		querytree_list = pg_analyze_and_rewrite(parsetree, NULL, 0);

		plantree_list = pg_plan_queries(querytree_list, true);

		/* If we got a cancel signal in analysis or planning, quit */
		CHECK_FOR_INTERRUPTS();

		/*
		 * Create unnamed portal to run the query or queries in. If there
		 * already is one, silently drop it.
		 */
		portal = CreatePortal("", true, true);

		PortalDefineQuery(portal,
						  query_string,
						  commandTag,
						  querytree_list,
						  plantree_list,
						  MessageContext);

		/*
		 * Start the portal.  No parameters here.
		 */
		PortalStart(portal, NULL);

		/*
		 * Select the appropriate output format: text unless we are doing
		 * a FETCH from a binary cursor.  (Pretty grotty to have to do
		 * this here --- but it avoids grottiness in other places.	Ah,
		 * the joys of backward compatibility...)
		 */
		format = 0;				/* TEXT is default */
		if (IsA(parsetree, FetchStmt))
		{
			FetchStmt  *stmt = (FetchStmt *) parsetree;

			if (!stmt->ismove)
			{
				Portal		fportal = GetPortalByName(stmt->portalname);

				if (PortalIsValid(fportal) &&
					(fportal->cursorOptions & CURSOR_OPT_BINARY))
					format = 1; /* BINARY */
			}
		}
		PortalSetResultFormat(portal, 1, &format);

		/*
		 * Now we can create the destination receiver object.
		 */
		receiver = CreateDestReceiver(dest, portal);

		/*
		 * Switch back to transaction context for execution.
		 */
		MemoryContextSwitchTo(oldcontext);

		/*
		 * Run the portal to completion, and then drop it (and the
		 * receiver).
		 */
		(void) PortalRun(portal,
						 FETCH_ALL,
						 receiver,
						 receiver,
						 completionTag);

		(*receiver->rDestroy) (receiver);

		PortalDrop(portal, false);

		if (IsA(parsetree, TransactionStmt))
		{
			/*
			 * If this was a transaction control statement, commit it. We
			 * will start a new xact command for the next command (if
			 * any).
			 */
			finish_xact_command();
		}
		else if (lnext(parsetree_item) == NIL)
		{
			/*
			 * If this is the last parsetree of the query string, close
			 * down transaction statement before reporting
			 * command-complete.  This is so that any end-of-transaction
			 * errors are reported before the command-complete message is
			 * issued, to avoid confusing clients who will expect either a
			 * command-complete message or an error, not one and then the
			 * other.  But for compatibility with historical Postgres
			 * behavior, we do not force a transaction boundary between
			 * queries appearing in a single query string.
			 */
			finish_xact_command();
		}
		else
		{
			/*
			 * We need a CommandCounterIncrement after every query, except
			 * those that start or end a transaction block.
			 */
			CommandCounterIncrement();
		}

		/*
		 * Tell client that we're done with this query.  Note we emit
		 * exactly one EndCommand report for each raw parsetree, thus one
		 * for each SQL command the client sent, regardless of rewriting.
		 * (But a command aborted by error will not send an EndCommand
		 * report at all.)
		 */
		EndCommand(completionTag, dest);
	}							/* end loop over parsetrees */

	/*
	 * Close down transaction statement, if one is open.
	 */
	finish_xact_command();

	/*
	 * If there were no parsetrees, return EmptyQueryResponse message.
	 */
	if (!parsetree_list)
		NullCommand(dest);

	QueryContext = NULL;

	/*
	 * Combine processing here as we need to calculate the query duration
	 * in both instances.
	 */
	if (save_log_duration || save_log_min_duration_statement != -1)
	{
		long		usecs;

		gettimeofday(&stop_t, NULL);
		if (stop_t.tv_usec < start_t.tv_usec)
		{
			stop_t.tv_sec--;
			stop_t.tv_usec += 1000000;
		}
		usecs = (long) (stop_t.tv_sec - start_t.tv_sec) * 1000000 + (long) (stop_t.tv_usec - start_t.tv_usec);

		if (save_log_duration)
			ereport(LOG,
					(errmsg("duration: %ld.%03ld ms",
							(long) ((stop_t.tv_sec - start_t.tv_sec) * 1000 +
							(stop_t.tv_usec - start_t.tv_usec) / 1000),
							(long) (stop_t.tv_usec - start_t.tv_usec) % 1000)));

		/*
		 * Output a duration_statement to the log if the query has exceeded
		 * the min duration, or if we are to print all durations.
		 */
		if (save_log_min_duration_statement == 0 ||
			(save_log_min_duration_statement > 0 &&
			 usecs >= save_log_min_duration_statement * 1000))
			ereport(LOG,
					(errmsg("duration: %ld.%03ld ms  statement: %s",
							(long) ((stop_t.tv_sec - start_t.tv_sec) * 1000 +
							(stop_t.tv_usec - start_t.tv_usec) / 1000),
							(long) (stop_t.tv_usec - start_t.tv_usec) % 1000,
							query_string)));
	}

	if (save_log_statement_stats)
		ShowUsage("QUERY STATISTICS");

	debug_query_string = NULL;
}

/*
 * exec_parse_message
 *
 * Execute a "Parse" protocol message.
 */
static void
exec_parse_message(const char *query_string,	/* string to execute */
				   const char *stmt_name,		/* name for prepared stmt */
				   Oid *paramTypes,		/* parameter types */
				   int numParams)		/* number of parameters */
{
	MemoryContext oldcontext;
	List	   *parsetree_list;
	const char *commandTag;
	List	   *querytree_list,
			   *plantree_list,
			   *param_list;
	bool		is_named;
	bool		save_log_statement_stats = log_statement_stats;

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

	pgstat_report_activity(query_string);

	set_ps_display("PARSE");

	if (save_log_statement_stats)
		ResetUsage();

	/*
	 * Start up a transaction command so we can run parse analysis etc.
	 * (Note that this will normally change current memory context.)
	 * Nothing happens if we are already in one.
	 */
	start_xact_command();

	/*