connect_utils.c

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/*-------------------------------------------------------------------------
 *
 * Facilities for frontend code to connect to and disconnect from databases.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/fe_utils/connect_utils.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"
 
#include "common/connect.h"
#include "common/logging.h"
#include "common/string.h"
#include "fe_utils/connect_utils.h"
#include "fe_utils/query_utils.h"
 
/*
 * Make a database connection with the given parameters.
 *
 * An interactive password prompt is automatically issued if needed and
 * allowed by cparams->prompt_password.
 *
 * If allow_password_reuse is true, we will try to re-use any password
 * given during previous calls to this routine.  (Callers should not pass
 * allow_password_reuse=true unless reconnecting to the same host+port+user
 * as before, else we might create password exposure hazards.)
 */
PGconn *
connectDatabase(const ConnParams *cparams, const char *progname,
                bool echo, bool fail_ok, bool allow_password_reuse)
{
    PGconn     *conn;
    bool        new_pass;
    static char *password = NULL;
 
    /* Callers must supply at least dbname; other params can be NULL */
    Assert(cparams->dbname);
 
    if (!allow_password_reuse && password)
    {
        free(password);
        password = NULL;
    }
 
    if (cparams->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->pguser;
        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;
        conn = PQconnectdbParams(keywords, values, true);
 
        if (!conn)
            pg_fatal("could not connect to database %s: out of memory",
                     cparams->dbname);
 
        /*
         * No luck?  Trying asking (again) for a password.
         */
        if (PQstatus(conn) == CONNECTION_BAD &&
            PQconnectionNeedsPassword(conn) &&
            cparams->prompt_password != TRI_NO)
        {
            PQfinish(conn);
            free(password);
            password = simple_prompt("Password: ", false);
            new_pass = true;
        }
    } while (new_pass);
 
    /* check to see that the backend connection was successfully made */
    if (PQstatus(conn) == CONNECTION_BAD)
    {
        if (fail_ok)
        {
            PQfinish(conn);
            return NULL;
        }
        pg_fatal("%s", PQerrorMessage(conn));
    }
 
    /* Start strict; callers may override this. */
    PQclear(executeQuery(conn, ALWAYS_SECURE_SEARCH_PATH_SQL, echo));
 
    return conn;
}
 
/*
 * Try to connect to the appropriate maintenance database.
 *
 * This differs from connectDatabase only in that it has a rule for
 * inserting a default "dbname" if none was given (which is why cparams
 * is not const).  Note that cparams->dbname should typically come from
 * a --maintenance-db command line parameter.
 */
PGconn *
connectMaintenanceDatabase(ConnParams *cparams,
                           const char *progname, bool echo)
{
    PGconn     *conn;
 
    /* If a maintenance database name was specified, just connect to it. */
    if (cparams->dbname)
        return connectDatabase(cparams, progname, echo, false, false);
 
    /* Otherwise, try postgres first and then template1. */
    cparams->dbname = "postgres";
    conn = connectDatabase(cparams, progname, echo, true, false);
    if (!conn)
    {
        cparams->dbname = "template1";
        conn = connectDatabase(cparams, progname, echo, false, false);
    }
    return conn;
}
 
/*
 * Disconnect the given connection, canceling any statement if one is active.
 */
void
disconnectDatabase(PGconn *conn)
{
    Assert(conn != NULL);
 
    if (PQtransactionStatus(conn) == PQTRANS_ACTIVE)
    {
        PGcancelConn *cancelConn = PQcancelCreate(conn);
 
        (void) PQcancelBlocking(cancelConn);
        PQcancelFinish(cancelConn);
    }
 
    PQfinish(conn);
}