postgres.c

来自「PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统」· C语言 代码 · 共 2,390 行 · 第 1/5 页

	List	   *querytree_list;
	ListCell   *list_item;

	/*
	 * (1) parse the request string into a list of raw parse trees.
	 */
	raw_parsetree_list = pg_parse_query(query_string);

	/*
	 * (2) Do parse analysis and rule rewrite.
	 */
	querytree_list = NIL;
	foreach(list_item, raw_parsetree_list)
	{
		Node	   *parsetree = (Node *) lfirst(list_item);

		querytree_list = list_concat(querytree_list,
									 pg_analyze_and_rewrite(parsetree,
															paramTypes,
															numParams));
	}

	return querytree_list;
}

/*
 * Do raw parsing (only).
 *
 * A list of parsetrees is returned, since there might be multiple
 * commands in the given string.
 *
 * NOTE: for interactive queries, it is important to keep this routine
 * separate from the analysis & rewrite stages.  Analysis and rewriting
 * cannot be done in an aborted transaction, since they require access to
 * database tables.  So, we rely on the raw parser to determine whether
 * we've seen a COMMIT or ABORT command; when we are in abort state, other
 * commands are not processed any further than the raw parse stage.
 */
List *
pg_parse_query(const char *query_string)
{
	List	   *raw_parsetree_list;

	if (log_parser_stats)
		ResetUsage();

	raw_parsetree_list = raw_parser(query_string);

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

	return raw_parsetree_list;
}

static bool
log_after_parse(List *raw_parsetree_list, const char *query_string,
				char **prepare_string)
{
	ListCell   *parsetree_item;
	bool		log_this_statement = (log_statement == LOGSTMT_ALL);

	*prepare_string = NULL;

	/* Check if we need to log the statement, and get prepare_string. */
	foreach(parsetree_item, raw_parsetree_list)
	{
		Node	   *parsetree = (Node *) lfirst(parsetree_item);
		const char *commandTag;

		if (IsA(parsetree, ExplainStmt) &&
			((ExplainStmt *) parsetree)->analyze)
			parsetree = (Node *) (((ExplainStmt *) parsetree)->query);

		if (IsA(parsetree, PrepareStmt))
			parsetree = (Node *) (((PrepareStmt *) parsetree)->query);

		if (IsA(parsetree, SelectStmt) &&
			((SelectStmt *) parsetree)->into == NULL)
			continue;			/* optimization for frequent command */

		if (log_statement == LOGSTMT_MOD &&
			(IsA(parsetree, InsertStmt) ||
			 IsA(parsetree, UpdateStmt) ||
			 IsA(parsetree, DeleteStmt) ||
			 IsA(parsetree, TruncateStmt) ||
			 (IsA(parsetree, CopyStmt) &&
			  ((CopyStmt *) parsetree)->is_from)))		/* COPY FROM */
			log_this_statement = true;

		commandTag = CreateCommandTag(parsetree);
		if ((log_statement == LOGSTMT_MOD ||
			 log_statement == LOGSTMT_DDL) &&
			(strncmp(commandTag, "CREATE ", strlen("CREATE ")) == 0 ||
			 IsA(parsetree, SelectStmt) ||		/* SELECT INTO, CREATE AS */
			 strncmp(commandTag, "ALTER ", strlen("ALTER ")) == 0 ||
			 strncmp(commandTag, "DROP ", strlen("DROP ")) == 0 ||
			 IsA(parsetree, GrantStmt) ||		/* GRANT or REVOKE */
			 IsA(parsetree, CommentStmt)))
			log_this_statement = true;

		/*
		 * For the first EXECUTE we find, record the client statement used by
		 * the PREPARE.  PREPARE doesn't save the parse tree so we have no
		 * way to conditionally output based on the type of query prepared.
		 */
		if (IsA(parsetree, ExecuteStmt))
		{
			ExecuteStmt *stmt = (ExecuteStmt *) parsetree;
			PreparedStatement *entry;

			if (*prepare_string == NULL &&
				(entry = FetchPreparedStatement(stmt->name, false)) != NULL &&
				entry->query_string)
			{
				*prepare_string = palloc(strlen(entry->query_string) +
									  strlen("  [PREPARE:  %s]") - 2 + 1);
				sprintf(*prepare_string, "  [PREPARE:  %s]",
						entry->query_string);
			}
		}
	}

	if (log_this_statement)
	{
		ereport(LOG,
				(errmsg("statement: %s%s", query_string,
						*prepare_string ? *prepare_string : "")));
		return true;
	}
	else
		return false;
}


/*
 * Given a raw parsetree (gram.y output), and optionally information about
 * types of parameter symbols ($n), perform parse analysis and rule rewriting.
 *
 * A list of Query nodes is returned, since either the analyzer or the
 * rewriter might expand one query to several.
 *
 * NOTE: for reasons mentioned above, this must be separate from raw parsing.
 */
List *
pg_analyze_and_rewrite(Node *parsetree, Oid *paramTypes, int numParams)
{
	List	   *querytree_list;

	/*
	 * (1) Perform parse analysis.
	 */
	if (log_parser_stats)
		ResetUsage();

	querytree_list = parse_analyze(parsetree, paramTypes, numParams);

	if (log_parser_stats)
		ShowUsage("PARSE ANALYSIS STATISTICS");

	/*
	 * (2) Rewrite the queries, as necessary
	 */
	querytree_list = pg_rewrite_queries(querytree_list);

	return querytree_list;
}

/*
 * Perform rewriting of a list of queries produced by parse analysis.
 *
 * Note: queries must just have come from the parser, because we do not do
 * AcquireRewriteLocks() on them.
 */
static List *
pg_rewrite_queries(List *querytree_list)
{
	List	   *new_list = NIL;
	ListCell   *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 = list_concat(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, ParamListInfo boundParams)
{
	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, boundParams);

	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, ParamListInfo boundParams,
				bool needSnapshot)
{
	List	   *plan_list = NIL;
	ListCell   *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)
			{
				ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
				needSnapshot = false;
			}
			plan = pg_plan_query(query, boundParams);
		}

		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;
	ListCell   *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;
	char	   *prepare_string = NULL;
	bool		was_logged = false;

	/*
	 * 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);

	if (log_statement != LOGSTMT_NONE || save_log_min_duration_statement != -1)
		was_logged = log_after_parse(parsetree_list, query_string,
									 &prepare_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() &&
			!IsTransactionExitStmt(parsetree))
			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, NULL, 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);