postgres.c

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/*-------------------------------------------------------------------------
 *
 * postgres.c
 *	  POSTGRES C Backend Interface
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.468.2.4 2006/04/18 00:52:41 momjian Exp $
 *
 * NOTES
 *	  this is the "main" module of the postgres backend and
 *	  hence the main module of the "traffic cop".
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/socket.h>
#if HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif

#include "access/printtup.h"
#include "access/xlog.h"
#include "catalog/pg_type.h"
#include "commands/async.h"
#include "commands/prepare.h"
#include "commands/trigger.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "nodes/print.h"
#include "optimizer/cost.h"
#include "optimizer/planner.h"
#include "parser/analyze.h"
#include "parser/parser.h"
#include "rewrite/rewriteHandler.h"
#include "storage/freespace.h"
#include "storage/ipc.h"
#include "storage/pg_shmem.h"
#include "storage/proc.h"
#include "storage/sinval.h"
#include "tcop/fastpath.h"
#include "tcop/pquery.h"
#include "tcop/tcopprot.h"
#include "tcop/utility.h"
#include "utils/flatfiles.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
#include "mb/pg_wchar.h"

#include "pgstat.h"

extern int	optind;
extern char *optarg;

/* ----------------
 *		global variables
 * ----------------
 */
const char *debug_query_string; /* for pgmonitor and log_min_error_statement */

/* Note: whereToSendOutput is initialized for the bootstrap/standalone case */
CommandDest whereToSendOutput = DestDebug;

/* flag for logging end of session */
bool		Log_disconnections = false;

LogStmtLevel log_statement = LOGSTMT_NONE;

/* GUC variable for maximum stack depth (measured in kilobytes) */
int			max_stack_depth = 2048;


/* ----------------
 *		private variables
 * ----------------
 */

/* max_stack_depth converted to bytes for speed of checking */
static int	max_stack_depth_bytes = 2048 * 1024;

/* stack base pointer (initialized by PostgresMain) */
/* Do not make static so PL/Java can modifiy it */
char	   *stack_base_ptr = NULL;


/*
 * Flag to mark SIGHUP. Whenever the main loop comes around it
 * will reread the configuration file. (Better than doing the
 * reading in the signal handler, ey?)
 */
static volatile sig_atomic_t got_SIGHUP = false;

/*
 * Flag to keep track of whether we have started a transaction.
 * For extended query protocol this has to be remembered across messages.
 */
static bool xact_started = false;

/*
 * Flag to indicate that we are doing the outer loop's read-from-client,
 * as opposed to any random read from client that might happen within
 * commands like COPY FROM STDIN.
 */
static bool DoingCommandRead = false;

/*
 * Flags to implement skip-till-Sync-after-error behavior for messages of
 * the extended query protocol.
 */
static bool doing_extended_query_message = false;
static bool ignore_till_sync = false;

/*
 * If an unnamed prepared statement exists, it's stored here.
 * We keep it separate from the hashtable kept by commands/prepare.c
 * in order to reduce overhead for short-lived queries.
 */
static MemoryContext unnamed_stmt_context = NULL;
static PreparedStatement *unnamed_stmt_pstmt = NULL;


static bool EchoQuery = false;	/* default don't echo */

/*
 * people who want to use EOF should #define DONTUSENEWLINE in
 * tcop/tcopdebug.h
 */
#ifndef TCOP_DONTUSENEWLINE
static int	UseNewLine = 1;		/* Use newlines query delimiters (the default) */
#else
static int	UseNewLine = 0;		/* Use EOF as query delimiters */
#endif   /* TCOP_DONTUSENEWLINE */


/* ----------------------------------------------------------------
 *		decls for routines only used in this file
 * ----------------------------------------------------------------
 */
static int	InteractiveBackend(StringInfo inBuf);
static int	SocketBackend(StringInfo inBuf);
static int	ReadCommand(StringInfo inBuf);
static bool log_after_parse(List *raw_parsetree_list,
				const char *query_string, char **prepare_string);
static List *pg_rewrite_queries(List *querytree_list);
static void start_xact_command(void);
static void finish_xact_command(void);
static bool IsTransactionExitStmt(Node *parsetree);
static bool IsTransactionExitStmtList(List *parseTrees);
static bool IsTransactionStmtList(List *parseTrees);
static void SigHupHandler(SIGNAL_ARGS);
static void log_disconnections(int code, Datum arg);


/* ----------------------------------------------------------------
 *		routines to obtain user input
 * ----------------------------------------------------------------
 */

/* ----------------
 *	InteractiveBackend() is called for user interactive connections
 *
 *	the string entered by the user is placed in its parameter inBuf,
 *	and we act like a Q message was received.
 *
 *	EOF is returned if end-of-file input is seen; time to shut down.
 * ----------------
 */

static int
InteractiveBackend(StringInfo inBuf)
{
	int			c;				/* character read from getc() */
	bool		end = false;	/* end-of-input flag */
	bool		backslashSeen = false;	/* have we seen a \ ? */

	/*
	 * display a prompt and obtain input from the user
	 */
	printf("backend> ");
	fflush(stdout);

	/* Reset inBuf to empty */
	inBuf->len = 0;
	inBuf->data[0] = '\0';
	inBuf->cursor = 0;

	for (;;)
	{
		if (UseNewLine)
		{
			/*
			 * if we are using \n as a delimiter, then read characters until
			 * the \n.
			 */
			while ((c = getc(stdin)) != EOF)
			{
				if (c == '\n')
				{
					if (backslashSeen)
					{
						/* discard backslash from inBuf */
						inBuf->data[--inBuf->len] = '\0';
						backslashSeen = false;
						continue;
					}
					else
					{
						/* keep the newline character */
						appendStringInfoChar(inBuf, '\n');
						break;
					}
				}
				else if (c == '\\')
					backslashSeen = true;
				else
					backslashSeen = false;

				appendStringInfoChar(inBuf, (char) c);
			}

			if (c == EOF)
				end = true;
		}
		else
		{
			/*
			 * otherwise read characters until EOF.
			 */
			while ((c = getc(stdin)) != EOF)
				appendStringInfoChar(inBuf, (char) c);

			if (inBuf->len == 0)
				end = true;
		}

		if (end)
			return EOF;

		/*
		 * otherwise we have a user query so process it.
		 */
		break;
	}

	/* Add '\0' to make it look the same as message case. */
	appendStringInfoChar(inBuf, (char) '\0');

	/*
	 * if the query echo flag was given, print the query..
	 */
	if (EchoQuery)
		printf("statement: %s\n", inBuf->data);
	fflush(stdout);

	return 'Q';
}

/* ----------------
 *	SocketBackend()		Is called for frontend-backend connections
 *
 *	Returns the message type code, and loads message body data into inBuf.
 *
 *	EOF is returned if the connection is lost.
 * ----------------
 */
static int
SocketBackend(StringInfo inBuf)
{
	int			qtype;

	/*
	 * Get message type code from the frontend.
	 */
	qtype = pq_getbyte();

	if (qtype == EOF)			/* frontend disconnected */
	{
		ereport(COMMERROR,
				(errcode(ERRCODE_PROTOCOL_VIOLATION),
				 errmsg("unexpected EOF on client connection")));
		return qtype;
	}

	/*
	 * Validate message type code before trying to read body; if we have lost
	 * sync, better to say "command unknown" than to run out of memory because
	 * we used garbage as a length word.
	 *
	 * This also gives us a place to set the doing_extended_query_message flag
	 * as soon as possible.
	 */
	switch (qtype)
	{
		case 'Q':				/* simple query */
			doing_extended_query_message = false;
			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
			{
				/* old style without length word; convert */
				if (pq_getstring(inBuf))
				{
					ereport(COMMERROR,
							(errcode(ERRCODE_PROTOCOL_VIOLATION),
							 errmsg("unexpected EOF on client connection")));
					return EOF;
				}
			}
			break;

		case 'F':				/* fastpath function call */
			/* we let fastpath.c cope with old-style input of this */
			doing_extended_query_message = false;
			break;

		case 'X':				/* terminate */
			doing_extended_query_message = false;
			ignore_till_sync = false;
			break;

		case 'B':				/* bind */
		case 'C':				/* close */
		case 'D':				/* describe */
		case 'E':				/* execute */
		case 'H':				/* flush */
		case 'P':				/* parse */
			doing_extended_query_message = true;
			/* these are only legal in protocol 3 */
			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
				ereport(FATAL,
						(errcode(ERRCODE_PROTOCOL_VIOLATION),
						 errmsg("invalid frontend message type %d", qtype)));
			break;

		case 'S':				/* sync */
			/* stop any active skip-till-Sync */
			ignore_till_sync = false;
			/* mark not-extended, so that a new error doesn't begin skip */
			doing_extended_query_message = false;
			/* only legal in protocol 3 */
			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
				ereport(FATAL,
						(errcode(ERRCODE_PROTOCOL_VIOLATION),
						 errmsg("invalid frontend message type %d", qtype)));
			break;

		case 'd':				/* copy data */
		case 'c':				/* copy done */
		case 'f':				/* copy fail */
			doing_extended_query_message = false;
			/* these are only legal in protocol 3 */
			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
				ereport(FATAL,
						(errcode(ERRCODE_PROTOCOL_VIOLATION),
						 errmsg("invalid frontend message type %d", qtype)));
			break;

		default:

			/*
			 * Otherwise we got garbage from the frontend.	We treat this as
			 * fatal because we have probably lost message boundary sync, and
			 * there's no good way to recover.
			 */
			ereport(FATAL,
					(errcode(ERRCODE_PROTOCOL_VIOLATION),
					 errmsg("invalid frontend message type %d", qtype)));
			break;
	}

	/*
	 * In protocol version 3, all frontend messages have a length word next
	 * after the type code; we can read the message contents independently of
	 * the type.
	 */
	if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
	{
		if (pq_getmessage(inBuf, 0))
			return EOF;			/* suitable message already logged */
	}

	return qtype;
}

/* ----------------
 *		ReadCommand reads a command from either the frontend or
 *		standard input, places it in inBuf, and returns the
 *		message type code (first byte of the message).
 *		EOF is returned if end of file.
 * ----------------
 */
static int
ReadCommand(StringInfo inBuf)
{
	int			result;

	if (whereToSendOutput == DestRemote)
		result = SocketBackend(inBuf);
	else
		result = InteractiveBackend(inBuf);
	return result;
}

/*
 * prepare_for_client_read -- set up to possibly block on client input
 *
 * This must be called immediately before any low-level read from the
 * client connection.  It is necessary to do it at a sufficiently low level
 * that there won't be any other operations except the read kernel call
 * itself between this call and the subsequent client_read_ended() call.
 * In particular there mustn't be use of malloc() or other potentially
 * non-reentrant libc functions.  This restriction makes it safe for us
 * to allow interrupt service routines to execute nontrivial code while
 * we are waiting for input.
 */
void
prepare_for_client_read(void)
{
	if (DoingCommandRead)
	{
		/* Enable immediate processing of asynchronous signals */
		EnableNotifyInterrupt();
		EnableCatchupInterrupt();

		/* Allow "die" interrupt to be processed while waiting */
		ImmediateInterruptOK = true;

		/* And don't forget to detect one that already arrived */
		QueryCancelPending = false;
		CHECK_FOR_INTERRUPTS();
	}
}

/*
 * client_read_ended -- get out of the client-input state
 */
void
client_read_ended(void)
{
	if (DoingCommandRead)
	{
		ImmediateInterruptOK = false;
		QueryCancelPending = false;		/* forget any CANCEL signal */

		DisableNotifyInterrupt();
		DisableCatchupInterrupt();
	}
}


/*
 * Parse a query string and pass it through the rewriter.
 *
 * A list of Query nodes is returned, since the string might contain
 * multiple queries and/or the rewriter might expand one query to several.
 *
 * NOTE: this routine is no longer used for processing interactive queries,
 * but it is still needed for parsing of SQL function bodies.
 */
List *
pg_parse_and_rewrite(const char *query_string,	/* string to execute */
					 Oid *paramTypes,	/* parameter types */
					 int numParams)		/* number of parameters */
{
	List	   *raw_parsetree_list;