pg_backup_db.c

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/*-------------------------------------------------------------------------
 *
 * pg_backup_db.c
 *
 *  Implements the basic DB functions used by the archiver.
 *
 * IDENTIFICATION
 *    src/bin/pg_dump/pg_backup_db.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"

#include <unistd.h>
#include <ctype.h>
#ifdef HAVE_TERMIOS_H
#include <termios.h>
#endif

#include "common/connect.h"
#include "common/string.h"
#include "dumputils.h"
#include "fe_utils/string_utils.h"
#include "parallel.h"
#include "pg_backup_archiver.h"
#include "pg_backup_db.h"
#include "pg_backup_utils.h"

static void _check_database_version(ArchiveHandle *AH);
static void notice_processor(void *arg, const char *message);

static void
_check_database_version(ArchiveHandle *AH)
{
    const char *remoteversion_str;
    int         remoteversion;
    PGresult   *res;

    remoteversion_str = PQparameterStatus(AH->connection, "server_version");
    remoteversion = PQserverVersion(AH->connection);
    if (remoteversion == 0 || !remoteversion_str)
        fatal("could not get server_version from libpq");

    AH->public.remoteVersionStr = pg_strdup(remoteversion_str);
    AH->public.remoteVersion = remoteversion;
    if (!AH->archiveRemoteVersion)
        AH->archiveRemoteVersion = AH->public.remoteVersionStr;

    if (remoteversion != PG_VERSION_NUM
        && (remoteversion < AH->public.minRemoteVersion ||
            remoteversion > AH->public.maxRemoteVersion))
    {
        pg_log_error("server version: %s; %s version: %s",
                     remoteversion_str, progname, PG_VERSION);
        fatal("aborting because of server version mismatch");
    }

    /*
     * When running against 9.0 or later, check if we are in recovery mode,
     * which means we are on a hot standby.
     */
    if (remoteversion >= 90000)
    {
        res = ExecuteSqlQueryForSingleRow((Archive *) AH, "SELECT pg_catalog.pg_is_in_recovery()");

        AH->public.isStandby = (strcmp(PQgetvalue(res, 0, 0), "t") == 0);
        PQclear(res);
    }
    else
        AH->public.isStandby = false;
}

/*
 * Reconnect to the server.  If dbname is not NULL, use that database,
 * else the one associated with the archive handle.
 */
void
ReconnectToServer(ArchiveHandle *AH, const char *dbname)
{
    PGconn     *oldConn = AH->connection;
    RestoreOptions *ropt = AH->public.ropt;

    /*
     * Save the dbname, if given, in override_dbname so that it will also
     * affect any later reconnection attempt.
     */
    if (dbname)
        ropt->cparams.override_dbname = pg_strdup(dbname);

    /*
     * Note: we want to establish the new connection, and in particular update
     * ArchiveHandle's connCancel, before closing old connection.  Otherwise
     * an ill-timed SIGINT could try to access a dead connection.
     */
    AH->connection = NULL;      /* dodge error check in ConnectDatabase */

    ConnectDatabase((Archive *) AH, &ropt->cparams, true);

    PQfinish(oldConn);
}

/*
 * Make, or remake, a database connection with the given parameters.
 *
 * The resulting connection handle is stored in AHX->connection.
 *
 * An interactive password prompt is automatically issued if required.
 * We store the results of that in AHX->savedPassword.
 * Note: it's not really all that sensible to use a single-entry password
 * cache if the username keeps changing.  In current usage, however, the
 * username never does change, so one savedPassword is sufficient.
 */
void
ConnectDatabase(Archive *AHX,
                const ConnParams *cparams,
                bool isReconnect)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;
    trivalue    prompt_password;
    char       *password;
    bool        new_pass;

    if (AH->connection)
        fatal("already connected to a database");

    /* Never prompt for a password during a reconnection */
    prompt_password = isReconnect ? TRI_NO : cparams->promptPassword;

    password = AH->savedPassword;

    if (prompt_password == TRI_YES && password == NULL)
        password = simple_prompt("Password: ", false);

    /*
     * Start the connection.  Loop until we have a password if requested by
     * backend.
     */
    do
    {
        const char *keywords[8];
        const char *values[8];
        int         i = 0;

        /*
         * If dbname is a connstring, its entries can override the other
         * values obtained from cparams; but in turn, override_dbname can
         * override the dbname component of it.
         */
        keywords[i] = "host";
        values[i++] = cparams->pghost;
        keywords[i] = "port";
        values[i++] = cparams->pgport;
        keywords[i] = "user";
        values[i++] = cparams->username;
        keywords[i] = "password";
        values[i++] = password;
        keywords[i] = "dbname";
        values[i++] = cparams->dbname;
        if (cparams->override_dbname)
        {
            keywords[i] = "dbname";
            values[i++] = cparams->override_dbname;
        }
        keywords[i] = "fallback_application_name";
        values[i++] = progname;
        keywords[i] = NULL;
        values[i++] = NULL;
        Assert(i <= lengthof(keywords));

        new_pass = false;
        AH->connection = PQconnectdbParams(keywords, values, true);

        if (!AH->connection)
            fatal("could not connect to database");

        if (PQstatus(AH->connection) == CONNECTION_BAD &&
            PQconnectionNeedsPassword(AH->connection) &&
            password == NULL &&
            prompt_password != TRI_NO)
        {
            PQfinish(AH->connection);
            password = simple_prompt("Password: ", false);
            new_pass = true;
        }
    } while (new_pass);

    /* check to see that the backend connection was successfully made */
    if (PQstatus(AH->connection) == CONNECTION_BAD)
    {
        if (isReconnect)
            fatal("reconnection failed: %s",
                  PQerrorMessage(AH->connection));
        else
            fatal("%s",
                  PQerrorMessage(AH->connection));
    }

    /* Start strict; later phases may override this. */
    PQclear(ExecuteSqlQueryForSingleRow((Archive *) AH,
                                        ALWAYS_SECURE_SEARCH_PATH_SQL));

    if (password && password != AH->savedPassword)
        free(password);

    /*
     * We want to remember connection's actual password, whether or not we got
     * it by prompting.  So we don't just store the password variable.
     */
    if (PQconnectionUsedPassword(AH->connection))
    {
        if (AH->savedPassword)
            free(AH->savedPassword);
        AH->savedPassword = pg_strdup(PQpass(AH->connection));
    }

    /* check for version mismatch */
    _check_database_version(AH);

    PQsetNoticeProcessor(AH->connection, notice_processor, NULL);

    /* arrange for SIGINT to issue a query cancel on this connection */
    set_archive_cancel_info(AH, AH->connection);
}

/*
 * Close the connection to the database and also cancel off the query if we
 * have one running.
 */
void
DisconnectDatabase(Archive *AHX)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;
    char        errbuf[1];

    if (!AH->connection)
        return;

    if (AH->connCancel)
    {
        /*
         * If we have an active query, send a cancel before closing, ignoring
         * any errors.  This is of no use for a normal exit, but might be
         * helpful during fatal().
         */
        if (PQtransactionStatus(AH->connection) == PQTRANS_ACTIVE)
            (void) PQcancel(AH->connCancel, errbuf, sizeof(errbuf));

        /*
         * Prevent signal handler from sending a cancel after this.
         */
        set_archive_cancel_info(AH, NULL);
    }

    PQfinish(AH->connection);
    AH->connection = NULL;
}

PGconn *
GetConnection(Archive *AHX)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;

    return AH->connection;
}

static void
notice_processor(void *arg, const char *message)
{
    pg_log_generic(PG_LOG_INFO, "%s", message);
}

/* Like fatal(), but with a complaint about a particular query. */
static void
die_on_query_failure(ArchiveHandle *AH, const char *query)
{
    pg_log_error("query failed: %s",
                 PQerrorMessage(AH->connection));
    fatal("query was: %s", query);
}

void
ExecuteSqlStatement(Archive *AHX, const char *query)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;
    PGresult   *res;

    res = PQexec(AH->connection, query);
    if (PQresultStatus(res) != PGRES_COMMAND_OK)
        die_on_query_failure(AH, query);
    PQclear(res);
}

PGresult *
ExecuteSqlQuery(Archive *AHX, const char *query, ExecStatusType status)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;
    PGresult   *res;

    res = PQexec(AH->connection, query);
    if (PQresultStatus(res) != status)
        die_on_query_failure(AH, query);
    return res;
}

/*
 * Execute an SQL query and verify that we got exactly one row back.
 */
PGresult *
ExecuteSqlQueryForSingleRow(Archive *fout, const char *query)
{
    PGresult   *res;
    int         ntups;

    res = ExecuteSqlQuery(fout, query, PGRES_TUPLES_OK);

    /* Expecting a single result only */
    ntups = PQntuples(res);
    if (ntups != 1)
        fatal(ngettext("query returned %d row instead of one: %s",
                       "query returned %d rows instead of one: %s",
                       ntups),
              ntups, query);

    return res;
}

/*
 * Convenience function to send a query.
 * Monitors result to detect COPY statements
 */
static void
ExecuteSqlCommand(ArchiveHandle *AH, const char *qry, const char *desc)
{
    PGconn     *conn = AH->connection;
    PGresult   *res;

#ifdef NOT_USED
    fprintf(stderr, "Executing: '%s'\n\n", qry);
#endif
    res = PQexec(conn, qry);

    switch (PQresultStatus(res))
    {
        case PGRES_COMMAND_OK:
        case PGRES_TUPLES_OK:
        case PGRES_EMPTY_QUERY:
            /* A-OK */
            break;
        case PGRES_COPY_IN:
            /* Assume this is an expected result */
            AH->pgCopyIn = true;
            break;
        default:
            /* trouble */
            warn_or_exit_horribly(AH, "%s: %sCommand was: %s",
                                  desc, PQerrorMessage(conn), qry);
            break;
    }

    PQclear(res);
}


/*
 * Process non-COPY table data (that is, INSERT commands).
 *
 * The commands have been run together as one long string for compressibility,
 * and we are receiving them in bufferloads with arbitrary boundaries, so we
 * have to locate command boundaries and save partial commands across calls.
 * All state must be kept in AH->sqlparse, not in local variables of this
 * routine.  We assume that AH->sqlparse was filled with zeroes when created.
 *
 * We have to lex the data to the extent of identifying literals and quoted
 * identifiers, so that we can recognize statement-terminating semicolons.
 * We assume that INSERT data will not contain SQL comments, E'' literals,
 * or dollar-quoted strings, so this is much simpler than a full SQL lexer.
 *
 * Note: when restoring from a pre-9.0 dump file, this code is also used to
 * process BLOB COMMENTS data, which has the same problem of containing
 * multiple SQL commands that might be split across bufferloads.  Fortunately,
 * that data won't contain anything complicated to lex either.
 */
static void
ExecuteSimpleCommands(ArchiveHandle *AH, const char *buf, size_t bufLen)
{
    const char *qry = buf;
    const char *eos = buf + bufLen;

    /* initialize command buffer if first time through */
    if (AH->sqlparse.curCmd == NULL)
        AH->sqlparse.curCmd = createPQExpBuffer();

    for (; qry < eos; qry++)
    {
        char        ch = *qry;

        /* For neatness, we skip any newlines between commands */
        if (!(ch == '\n' && AH->sqlparse.curCmd->len == 0))
            appendPQExpBufferChar(AH->sqlparse.curCmd, ch);

        switch (AH->sqlparse.state)
        {
            case SQL_SCAN:      /* Default state == 0, set in _allocAH */
                if (ch == ';')
                {
                    /*
                     * We've found the end of a statement. Send it and reset
                     * the buffer.
                     */
                    ExecuteSqlCommand(AH, AH->sqlparse.curCmd->data,
                                      "could not execute query");
                    resetPQExpBuffer(AH->sqlparse.curCmd);
                }
                else if (ch == '\'')
                {
                    AH->sqlparse.state = SQL_IN_SINGLE_QUOTE;
                    AH->sqlparse.backSlash = false;
                }
                else if (ch == '"')
                {
                    AH->sqlparse.state = SQL_IN_DOUBLE_QUOTE;
                }
                break;

            case SQL_IN_SINGLE_QUOTE:
                /* We needn't handle '' specially */
                if (ch == '\'' && !AH->sqlparse.backSlash)
                    AH->sqlparse.state = SQL_SCAN;
                else if (ch == '\\' && !AH->public.std_strings)
                    AH->sqlparse.backSlash = !AH->sqlparse.backSlash;
                else
                    AH->sqlparse.backSlash = false;
                break;

            case SQL_IN_DOUBLE_QUOTE:
                /* We needn't handle "" specially */
                if (ch == '"')
                    AH->sqlparse.state = SQL_SCAN;
                break;
        }
    }
}


/*
 * Implement ahwrite() for direct-to-DB restore
 */
int
ExecuteSqlCommandBuf(Archive *AHX, const char *buf, size_t bufLen)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;

    if (AH->outputKind == OUTPUT_COPYDATA)
    {
        /*
         * COPY data.
         *
         * We drop the data on the floor if libpq has failed to enter COPY
         * mode; this allows us to behave reasonably when trying to continue
         * after an error in a COPY command.
         */
        if (AH->pgCopyIn &&
            PQputCopyData(AH->connection, buf, bufLen) <= 0)
            fatal("error returned by PQputCopyData: %s",
                  PQerrorMessage(AH->connection));
    }
    else if (AH->outputKind == OUTPUT_OTHERDATA)
    {
        /*
         * Table data expressed as INSERT commands; or, in old dump files,
         * BLOB COMMENTS data (which is expressed as COMMENT ON commands).
         */
        ExecuteSimpleCommands(AH, buf, bufLen);
    }
    else
    {
        /*
         * General SQL commands; we assume that commands will not be split
         * across calls.
         *
         * In most cases the data passed to us will be a null-terminated
         * string, but if it's not, we have to add a trailing null.
         */
        if (buf[bufLen] == '\0')
            ExecuteSqlCommand(AH, buf, "could not execute query");
        else
        {
            char       *str = (char *) pg_malloc(bufLen + 1);

            memcpy(str, buf, bufLen);
            str[bufLen] = '\0';
            ExecuteSqlCommand(AH, str, "could not execute query");
            free(str);
        }
    }

    return bufLen;
}

/*
 * Terminate a COPY operation during direct-to-DB restore
 */
void
EndDBCopyMode(Archive *AHX, const char *tocEntryTag)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;

    if (AH->pgCopyIn)
    {
        PGresult   *res;

        if (PQputCopyEnd(AH->connection, NULL) <= 0)
            fatal("error returned by PQputCopyEnd: %s",
                  PQerrorMessage(AH->connection));

        /* Check command status and return to normal libpq state */
        res = PQgetResult(AH->connection);
        if (PQresultStatus(res) != PGRES_COMMAND_OK)
            warn_or_exit_horribly(AH, "COPY failed for table \"%s\": %s",
                                  tocEntryTag, PQerrorMessage(AH->connection));
        PQclear(res);

        /* Do this to ensure we've pumped libpq back to idle state */
        if (PQgetResult(AH->connection) != NULL)
            pg_log_warning("unexpected extra results during COPY of table \"%s\"",
                           tocEntryTag);

        AH->pgCopyIn = false;
    }
}

void
StartTransaction(Archive *AHX)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;

    ExecuteSqlCommand(AH, "BEGIN", "could not start database transaction");
}

void
CommitTransaction(Archive *AHX)
{
    ArchiveHandle *AH = (ArchiveHandle *) AHX;

    ExecuteSqlCommand(AH, "COMMIT", "could not commit database transaction");
}

void
DropBlobIfExists(ArchiveHandle *AH, Oid oid)
{
    /*
     * If we are not restoring to a direct database connection, we have to
     * guess about how to detect whether the blob exists.  Assume new-style.
     */
    if (AH->connection == NULL ||
        PQserverVersion(AH->connection) >= 90000)
    {
        ahprintf(AH,
                 "SELECT pg_catalog.lo_unlink(oid) "
                 "FROM pg_catalog.pg_largeobject_metadata "
                 "WHERE oid = '%u';\n",
                 oid);
    }
    else
    {
        /* Restoring to pre-9.0 server, so do it the old way */
        ahprintf(AH,
                 "SELECT CASE WHEN EXISTS("
                 "SELECT 1 FROM pg_catalog.pg_largeobject WHERE loid = '%u'"
                 ") THEN pg_catalog.lo_unlink('%u') END;\n",
                 oid, oid);
    }
}