/*      $NetBSD: pgfs_db.c,v 1.3 2012/04/11 14:27:43 yamt Exp $ */

/*-
 * Copyright (c)2010,2011 YAMAMOTO Takashi,
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * backend db operations
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: pgfs_db.c,v 1.3 2012/04/11 14:27:43 yamt Exp $");
#endif /* not lint */

#include <assert.h>
#include <err.h>
#include <errno.h>
#include <inttypes.h>
#include <puffs.h>
#include <stdbool.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <util.h>

#include <libpq-fe.h>

#include "pgfs_db.h"
#include "pgfs_waitq.h"
#include "pgfs_debug.h"

bool pgfs_dosync = false;

struct Xconn {
        TAILQ_ENTRY(Xconn) list;
        PGconn *conn;
        struct puffs_cc *blocker;
        struct puffs_cc *owner;
        bool in_trans;
        int id;
        const char *label;
};

static void
dumperror(struct Xconn *xc, const PGresult *res)
{
        static const struct {
                const char *name;
                int code;
        } fields[] = {
#define F(x)    { .name = #x, .code = x, }
                F(PG_DIAG_SEVERITY),
                F(PG_DIAG_SQLSTATE),
                F(PG_DIAG_MESSAGE_PRIMARY),
                F(PG_DIAG_MESSAGE_DETAIL),
                F(PG_DIAG_MESSAGE_HINT),
                F(PG_DIAG_STATEMENT_POSITION),
                F(PG_DIAG_INTERNAL_POSITION),
                F(PG_DIAG_INTERNAL_QUERY),
                F(PG_DIAG_CONTEXT),
                F(PG_DIAG_SOURCE_FILE),
                F(PG_DIAG_SOURCE_LINE),
                F(PG_DIAG_SOURCE_FUNCTION),
#undef F
        };
        unsigned int i;

        if (!pgfs_dodprintf) {
                return;
        }
        assert(PQresultStatus(res) == PGRES_NONFATAL_ERROR ||
            PQresultStatus(res) == PGRES_FATAL_ERROR);
        for (i = 0; i < __arraycount(fields); i++) {
                const char *val = PQresultErrorField(res, fields[i].code);

                if (val == NULL) {
                        continue;
                }
                fprintf(stderr, "%s: %s\n", fields[i].name, val);
        }
}

TAILQ_HEAD(, Xconn) xclist = TAILQ_HEAD_INITIALIZER(xclist);
struct waitq xcwaitq = TAILQ_HEAD_INITIALIZER(xcwaitq);

static struct Xconn *
getxc(struct puffs_cc *cc)
{
        struct Xconn *xc;

        assert(cc != NULL);
retry:
        TAILQ_FOREACH(xc, &xclist, list) {
                if (xc->blocker == NULL) {
                        assert(xc->owner == NULL);
                        xc->owner = cc;
                        DPRINTF("xc %p acquire %p\n", xc, cc);
                        return xc;
                } else {
                        assert(xc->owner == xc->blocker);
                }
        }
        DPRINTF("no free conn %p\n", cc);
        waiton(&xcwaitq, cc);
        goto retry;
}

static void
relxc(struct Xconn *xc)
{

        assert(xc->in_trans);
        assert(xc->owner != NULL);
        xc->in_trans = false;
        xc->owner = NULL;
        wakeup_one(&xcwaitq);
}

static void
pqwait(struct Xconn *xc)
{
        PGconn *conn = xc->conn;
        struct puffs_cc *cc = xc->owner;

        if (PQflush(conn)) {
                errx(EXIT_FAILURE, "PQflush: %s", PQerrorMessage(conn));
        }
        if (!PQisBusy(conn)) {
                return;
        }
        assert(xc->blocker == NULL);
        xc->blocker = cc;
        DPRINTF("yielding %p\n", cc);
        /* XXX is it safe to yield before entering mainloop? */
        puffs_cc_yield(cc);
        DPRINTF("yield returned %p\n", cc);
        assert(xc->owner == cc);
        assert(xc->blocker == cc);
        xc->blocker = NULL;
}

static int
sqltoerrno(const char *sqlstate)
{
        /*
         * XXX hack; ERRCODE_INTERNAL_ERROR -> EAGAIN to handle
         * "tuple concurrently updated" errors for lowrite/lo_truncate.
         *
         * XXX should map ERRCODE_OUT_OF_MEMORY to EAGAIN?
         */
        static const struct {
                char sqlstate[5];
                int error;
        } map[] = {
                { "00000", 0, },        /* ERRCODE_SUCCESSFUL_COMPLETION */
                { "02000", ENOENT, },   /* ERRCODE_NO_DATA */
                { "23505", EEXIST, },   /* ERRCODE_UNIQUE_VIOLATION */
                { "23514", EINVAL, },   /* ERRCODE_CHECK_VIOLATION */
                { "40001", EAGAIN, },   /* ERRCODE_T_R_SERIALIZATION_FAILURE */
                { "40P01", EAGAIN, },   /* ERRCODE_T_R_DEADLOCK_DETECTED */
                { "42704", ENOENT, },   /* ERRCODE_UNDEFINED_OBJECT */
                { "53100", ENOSPC, },   /* ERRCODE_DISK_FULL */
                { "53200", ENOMEM, },   /* ERRCODE_OUT_OF_MEMORY */
                { "XX000", EAGAIN, },   /* ERRCODE_INTERNAL_ERROR */
        };
        unsigned int i;

        for (i = 0; i < __arraycount(map); i++) {
                if (!memcmp(map[i].sqlstate, sqlstate, 5)) {
                        const int error = map[i].error;

                        if (error != 0) {
                                DPRINTF("sqlstate %5s mapped to error %d\n",
                                    sqlstate, error);
                        }
                        if (error == EINVAL) {
                                /*
                                 * sounds like a bug.
                                 */
                                abort();
                        }
                        return error;
                }
        }
        DPRINTF("unknown sqlstate %5s mapped to EIO\n", sqlstate);
        return EIO;
}

struct cmd {
        char name[32];          /* name of prepared statement */
        char *cmd;              /* query string */
        unsigned int nparams;
        Oid *paramtypes;
        uint32_t prepared_mask; /* for which connections this is prepared? */
        unsigned int flags;     /* CMD_ flags */
};

#define CMD_NOPREPARE   1       /* don't prepare this command */

struct cmd *
createcmd(const char *cmd, unsigned int flags, ...)
{
        struct cmd *c;
        va_list ap;
        const char *cp;
        unsigned int i;
        static unsigned int cmdid;

        c = emalloc(sizeof(*c));
        c->cmd = estrdup(cmd);
        c->nparams = 0;
        va_start(ap, flags);
        for (cp = cmd; *cp != 0; cp++) {
                if (*cp == '$') { /* XXX */
                        c->nparams++;
                }
        }
        c->paramtypes = emalloc(c->nparams * sizeof(*c->paramtypes));
        for (i = 0; i < c->nparams; i++) {
                Oid type = va_arg(ap, Oid);
                assert(type == BYTEA ||
                    type == INT4OID || type == INT8OID || type == OIDOID ||
                    type == TEXTOID || type == TIMESTAMPTZOID);
                c->paramtypes[i] = type;
        }
        va_end(ap);
        snprintf(c->name, sizeof(c->name), "%u", cmdid++);
        if ((flags & CMD_NOPREPARE) != 0) {
                c->prepared_mask = ~0;
        } else {
                c->prepared_mask = 0;
        }
        c->flags = flags;
        return c;
}

static void
freecmd(struct cmd *c)
{

        free(c->paramtypes);
        free(c->cmd);
        free(c);
}

static int
fetch_noresult(struct Xconn *xc)
{
        PGresult *res;
        ExecStatusType status;
        PGconn *conn = xc->conn;
        int error;

        pqwait(xc);
        res = PQgetResult(conn);
        if (res == NULL) {
                return ENOENT;
        }
        status = PQresultStatus(res);
        if (status == PGRES_COMMAND_OK) {
                assert(PQnfields(res) == 0);
                assert(PQntuples(res) == 0);
                if (!strcmp(PQcmdTuples(res), "0")) {
                        error = ENOENT;
                } else {
                        error = 0;
                }
        } else if (status == PGRES_FATAL_ERROR) {
                error = sqltoerrno(PQresultErrorField(res, PG_DIAG_SQLSTATE));
                assert(error != 0);
                dumperror(xc, res);
        } else {
                errx(1, "%s not command_ok: %d: %s", __func__,
                    (int)status,
                    PQerrorMessage(conn));
        }
        PQclear(res);
        res = PQgetResult(conn);
        assert(res == NULL);
        if (error != 0) {
                DPRINTF("error %d\n", error);
        }
        return error;
}

static int
preparecmd(struct Xconn *xc, struct cmd *c)
{
        PGconn *conn = xc->conn;
        const uint32_t mask = 1 << xc->id;
        int error;
        int ret;

        if ((c->prepared_mask & mask) != 0) {
                return 0;
        }
        assert((c->flags & CMD_NOPREPARE) == 0);
        DPRINTF("PREPARE: '%s'\n", c->cmd);
        ret = PQsendPrepare(conn, c->name, c->cmd, c->nparams, c->paramtypes);
        if (!ret) {
                errx(EXIT_FAILURE, "PQsendPrepare: %s",
                    PQerrorMessage(conn));
        }
        error = fetch_noresult(xc);
        if (error != 0) {
                return error;
        }
        c->prepared_mask |= mask;
        return 0;
}

/*
 * vsendcmd:
 *
 * resultmode is just passed to PQsendQueryParams/PQsendQueryPrepared.
 * 0 for text and 1 for binary.
 */

static int
vsendcmd(struct Xconn *xc, int resultmode, struct cmd *c, va_list ap)
{
        PGconn *conn = xc->conn;
        char **paramvalues;
        int *paramlengths;
        int *paramformats;
        unsigned int i;
        int error;
        int ret;

        assert(xc->owner != NULL);
        assert(xc->blocker == NULL);
        error = preparecmd(xc, c);
        if (error != 0) {
                return error;
        }
        paramvalues = emalloc(c->nparams * sizeof(*paramvalues));
        paramlengths = NULL;
        paramformats = NULL;
        DPRINTF("CMD: '%s'\n", c->cmd);
        for (i = 0; i < c->nparams; i++) {
                Oid type = c->paramtypes[i];
                char tmpstore[1024];
                const char *buf = NULL;
                intmax_t v = 0; /* XXXgcc */
                int sz;
                bool binary = false;

                switch (type) {
                case BYTEA:
                        buf = va_arg(ap, const void *);
                        sz = (int)va_arg(ap, size_t);
                        binary = true;
                        break;
                case INT8OID:
                case OIDOID:
                case INT4OID:
                        switch (type) {
                        case INT8OID:
                                v = (intmax_t)va_arg(ap, int64_t);
                                break;
                        case OIDOID:
                                v = (intmax_t)va_arg(ap, Oid);
                                break;
                        case INT4OID:
                                v = (intmax_t)va_arg(ap, int32_t);
                                break;
                        default:
                                errx(EXIT_FAILURE, "unknown integer oid %u",
                                    type);
                        }
                        buf = tmpstore;
                        sz = snprintf(tmpstore, sizeof(tmpstore),
                            "%jd", v);
                        assert(sz != -1);
                        assert((size_t)sz < sizeof(tmpstore));
                        sz += 1;
                        break;
                case TEXTOID:
                case TIMESTAMPTZOID:
                        buf = va_arg(ap, char *);
                        sz = strlen(buf) + 1;
                        break;
                default:
                        errx(EXIT_FAILURE, "%s: unknown param type %u",
                            __func__, type);
                }
                if (binary) {
                        if (paramlengths == NULL) {
                                paramlengths =
                                    emalloc(c->nparams * sizeof(*paramformats));
                        }
                        if (paramformats == NULL) {
                                paramformats = ecalloc(1,
                                    c->nparams * sizeof(*paramformats));
                        }
                        paramformats[i] = 1;
                        paramlengths[i] = sz;
                }
                paramvalues[i] = emalloc(sz);
                memcpy(paramvalues[i], buf, sz);
                if (binary) {
                        DPRINTF("\t[%u]=<BINARY>\n", i);
                } else {
                        DPRINTF("\t[%u]='%s'\n", i, paramvalues[i]);
                }
        }
        if ((c->flags & CMD_NOPREPARE) != 0) {
                ret = PQsendQueryParams(conn, c->cmd, c->nparams, c->paramtypes,
                    (const char * const *)paramvalues, paramlengths,
                    paramformats, resultmode);
        } else {
                ret = PQsendQueryPrepared(conn, c->name, c->nparams,
                    (const char * const *)paramvalues, paramlengths,
                    paramformats, resultmode);
        }
        for (i = 0; i < c->nparams; i++) {
                free(paramvalues[i]);
        }
        free(paramvalues);
        free(paramlengths);
        free(paramformats);
        if (!ret) {
                errx(EXIT_FAILURE, "PQsendQueryPrepared: %s",
                    PQerrorMessage(conn));
        }
        return 0;
}

int
sendcmd(struct Xconn *xc, struct cmd *c, ...)
{
        va_list ap;
        int error;

        va_start(ap, c);
        error = vsendcmd(xc, 0, c, ap);
        va_end(ap);
        return error;
}

int
sendcmdx(struct Xconn *xc, int resultmode, struct cmd *c, ...)
{
        va_list ap;
        int error;

        va_start(ap, c);
        error = vsendcmd(xc, resultmode, c, ap);
        va_end(ap);
        return error;
}

/*
 * simplecmd: a convenient routine to execute a command which returns
 * no rows synchronously.
 */

int
simplecmd(struct Xconn *xc, struct cmd *c, ...)
{
        va_list ap;
        int error;

        va_start(ap, c);
        error = vsendcmd(xc, 0, c, ap);
        va_end(ap);
        if (error != 0) {
                return error;
        }
        return fetch_noresult(xc);
}

void
fetchinit(struct fetchstatus *s, struct Xconn *xc)
{
        s->xc = xc;
        s->res = NULL;
        s->cur = 0;
        s->nrows = 0;
        s->done = false;
}

static intmax_t
getint(const char *str)
{
        intmax_t i;
        char *ep;

        errno = 0;
        i = strtoimax(str, &ep, 10);
        assert(errno == 0);
        assert(str[0] != 0);
        assert(*ep == 0);
        return i;
}

static int
vfetchnext(struct fetchstatus *s, unsigned int n, const Oid *types, va_list ap)
{
        PGconn *conn = s->xc->conn;
        unsigned int i;

        assert(conn != NULL);
        if (s->res == NULL) {
                ExecStatusType status;
                int error;

                pqwait(s->xc);
                s->res = PQgetResult(conn);
                if (s->res == NULL) {
                        s->done = true;
                        return ENOENT;
                }
                status = PQresultStatus(s->res);
                if (status == PGRES_FATAL_ERROR) {
                        error = sqltoerrno(
                            PQresultErrorField(s->res, PG_DIAG_SQLSTATE));
                        assert(error != 0);
                        dumperror(s->xc, s->res);
                        return error;
                }
                if (status != PGRES_TUPLES_OK) {
                        errx(1, "not tuples_ok: %s",
                            PQerrorMessage(conn));
                }
                assert((unsigned int)PQnfields(s->res) == n);
                s->nrows = PQntuples(s->res);
                if (s->nrows == 0) {
                        DPRINTF("no rows\n");
                        return ENOENT;
                }
                assert(s->nrows >= 1);
                s->cur = 0;
        }
        for (i = 0; i < n; i++) {
                size_t size;

                assert((types[i] != BYTEA) == (PQfformat(s->res, i) == 0));
                DPRINTF("[%u] PQftype = %d, types = %d, value = '%s'\n",
                    i, PQftype(s->res, i), types[i],
                    PQgetisnull(s->res, s->cur, i) ? "<NULL>" :
                    PQfformat(s->res, i) == 0 ? PQgetvalue(s->res, s->cur, i) :
                    "<BINARY>");
                assert(PQftype(s->res, i) == types[i]);
                assert(!PQgetisnull(s->res, s->cur, i));
                switch(types[i]) {
                case INT8OID:
                        *va_arg(ap, int64_t *) =
                            getint(PQgetvalue(s->res, s->cur, i));
                        break;
                case OIDOID:
                        *va_arg(ap, Oid *) =
                            getint(PQgetvalue(s->res, s->cur, i));
                        break;
                case INT4OID:
                        *va_arg(ap, int32_t *) =
                            getint(PQgetvalue(s->res, s->cur, i));
                        break;
                case TEXTOID:
                        *va_arg(ap, char **) =
                            estrdup(PQgetvalue(s->res, s->cur, i));
                        break;
                case BYTEA:
                        size = PQgetlength(s->res, s->cur, i);
                        memcpy(va_arg(ap, void *),
                            PQgetvalue(s->res, s->cur, i), size);
                        *va_arg(ap, size_t *) = size;
                        break;
                default:
                        errx(EXIT_FAILURE, "%s unknown type %u", __func__,
                            types[i]);
                }
        }
        s->cur++;
        if (s->cur == s->nrows) {
                PQclear(s->res);
                s->res = NULL;
        }
        return 0;
}

int
fetchnext(struct fetchstatus *s, unsigned int n, const Oid *types, ...)
{
        va_list ap;
        int error;

        va_start(ap, types);
        error = vfetchnext(s, n, types, ap);
        va_end(ap);
        return error;
}

void
fetchdone(struct fetchstatus *s)
{

        if (s->res != NULL) {
                PQclear(s->res);
                s->res = NULL;
        }
        if (!s->done) {
                PGresult *res;
                unsigned int n;

                n = 0;
                while ((res = PQgetResult(s->xc->conn)) != NULL) {
                        PQclear(res);
                        n++;
                }
                if (n > 0) {
                        DPRINTF("%u rows dropped\n", n);
                }
        }
}

int
simplefetch(struct Xconn *xc, Oid type, ...)
{
        struct fetchstatus s;
        va_list ap;
        int error;

        fetchinit(&s, xc);
        va_start(ap, type);
        error = vfetchnext(&s, 1, &type, ap);
        va_end(ap);
        assert(error != 0 || s.res == NULL);
        fetchdone(&s);
        return error;
}

/*
 * setlabel: set the descriptive label for the connection.
 *
 * we use simple pointer comparison for label equality check.
 */
static void
setlabel(struct Xconn *xc, const char *label)
{
        int error;

        /*
         * put the label into application_name so that it's shown in
         * pg_stat_activity.  we are sure that our labels don't need
         * PQescapeStringConn.
         *
         * example:
         *      SELECT pid,application_name,query FROM pg_stat_activity
         *      WHERE state <> 'idle'
         */

        if (label != NULL && label != xc->label) {
                struct cmd *c;
                char cmd_str[1024];

                snprintf(cmd_str, sizeof(cmd_str),
                    "SET application_name TO 'pgfs: %s'", label);
                c = createcmd(cmd_str, CMD_NOPREPARE);
                error = simplecmd(xc, c);
                freecmd(c);
                assert(error == 0);
                xc->label = label;
        } else {
#if 0 /* don't bother to clear label */
                static struct cmd *c;

                CREATECMD_NOPARAM(c, "SET application_name TO 'pgfs'");
                error = simplecmd(xc, c);
                assert(error == 0);
#endif
        }
}

struct Xconn *
begin(struct puffs_usermount *pu, const char *label)
{
        struct Xconn *xc = getxc(puffs_cc_getcc(pu));
        static struct cmd *c;
        int error;

        setlabel(xc, label);
        CREATECMD_NOPARAM(c, "BEGIN");
        assert(!xc->in_trans);
        error = simplecmd(xc, c);
        assert(error == 0);
        assert(PQtransactionStatus(xc->conn) == PQTRANS_INTRANS);
        xc->in_trans = true;
        return xc;
}

struct Xconn *
begin_readonly(struct puffs_usermount *pu, const char *label)
{
        struct Xconn *xc = getxc(puffs_cc_getcc(pu));
        static struct cmd *c;
        int error;

        setlabel(xc, label);
        CREATECMD_NOPARAM(c, "BEGIN READ ONLY");
        assert(!xc->in_trans);
        error = simplecmd(xc, c);
        assert(error == 0);
        assert(PQtransactionStatus(xc->conn) == PQTRANS_INTRANS);
        xc->in_trans = true;
        return xc;
}

void
rollback(struct Xconn *xc)
{
        PGTransactionStatusType status;

        /*
         * check the status as we are not sure the status of our transaction
         * after a failed commit.
         */
        status = PQtransactionStatus(xc->conn);
        assert(status != PQTRANS_ACTIVE);
        assert(status != PQTRANS_UNKNOWN);
        if (status != PQTRANS_IDLE) {
                static struct cmd *c;
                int error;

                assert(status == PQTRANS_INTRANS || status == PQTRANS_INERROR);
                CREATECMD_NOPARAM(c, "ROLLBACK");
                error = simplecmd(xc, c);
                assert(error == 0);
        }
        DPRINTF("xc %p rollback %p\n", xc, xc->owner);
        setlabel(xc, NULL);
        relxc(xc);
}

int
commit(struct Xconn *xc)
{
        static struct cmd *c;
        int error;

        CREATECMD_NOPARAM(c, "COMMIT");
        error = simplecmd(xc, c);
        setlabel(xc, NULL);
        if (error == 0) {
                DPRINTF("xc %p commit %p\n", xc, xc->owner);
                relxc(xc);
        }
        return error;
}

int
commit_sync(struct Xconn *xc)
{
        static struct cmd *c;
        int error;

        assert(!pgfs_dosync);
        CREATECMD_NOPARAM(c, "SET LOCAL SYNCHRONOUS_COMMIT TO ON");
        error = simplecmd(xc, c);
        assert(error == 0);
        return commit(xc);
}

static void
pgfs_notice_receiver(void *vp, const PGresult *res)
{
        struct Xconn *xc = vp;

        assert(PQresultStatus(res) == PGRES_NONFATAL_ERROR);
        fprintf(stderr, "got a notice on %p\n", xc);
        dumperror(xc, res);
}

static int
pgfs_readframe(struct puffs_usermount *pu, struct puffs_framebuf *pufbuf,
    int fd, int *done)
{
        struct Xconn *xc;
        PGconn *conn;

        TAILQ_FOREACH(xc, &xclist, list) {
                if (PQsocket(xc->conn) == fd) {
                        break;
                }
        }
        assert(xc != NULL);
        conn = xc->conn;
        PQconsumeInput(conn);
        if (!PQisBusy(conn)) {
                if (xc->blocker != NULL) {
                        DPRINTF("schedule %p\n", xc->blocker);
                        puffs_cc_schedule(xc->blocker);
                } else {
                        DPRINTF("no blockers\n");
                }
        }
        *done = 0;
        return 0;
}

int
pgfs_connectdb(struct puffs_usermount *pu, const char *dbname,
    const char *dbuser, bool debug, bool synchronous, unsigned int nconn)
{
        const char *keywords[3+1];
        const char *values[3];
        unsigned int i;

        if (nconn > 32) {
                /*
                 * limit from sizeof(cmd->prepared_mask)
                 */
                return EINVAL;
        }
        if (debug) {
                pgfs_dodprintf = true;
        }
        if (synchronous) {
                pgfs_dosync = true;
        }
        i = 0;
        if (dbname != NULL) {
                keywords[i] = "dbname";
                values[i] = dbname;
                i++;
        }
        if (dbuser != NULL) {
                keywords[i] = "user";
                values[i] = dbuser;
                i++;
        }
        keywords[i] = "application_name";
        values[i] = "pgfs";
        i++;
        keywords[i] = NULL;
        puffs_framev_init(pu, pgfs_readframe, NULL, NULL, NULL, NULL);
        for (i = 0; i < nconn; i++) {
                struct Xconn *xc;
                struct Xconn *xc2;
                static int xcid;
                PGconn *conn;
                struct cmd *c;
                int error;

                conn = PQconnectdbParams(keywords, values, 0);
                if (conn == NULL) {
                        errx(EXIT_FAILURE,
                            "PQconnectdbParams: unknown failure");
                }
                if (PQstatus(conn) != CONNECTION_OK) {
                        /*
                         * XXX sleep and retry on ERRCODE_CANNOT_CONNECT_NOW
                         */
                        errx(EXIT_FAILURE, "PQconnectdbParams: %s",
                            PQerrorMessage(conn));
                }
                DPRINTF("protocol version %d\n", PQprotocolVersion(conn));
                puffs_framev_addfd(pu, PQsocket(conn), PUFFS_FBIO_READ);
                xc = emalloc(sizeof(*xc));
                xc->conn = conn;
                xc->blocker = NULL;
                xc->owner = NULL;
                xc->in_trans = false;
                xc->id = xcid++;
                xc->label = NULL;
                assert(xc->id < 32);
                PQsetNoticeReceiver(conn, pgfs_notice_receiver, xc);
                TAILQ_INSERT_HEAD(&xclist, xc, list);
                xc2 = begin(pu, NULL);
                assert(xc2 == xc);
                c = createcmd("SET search_path TO pgfs", CMD_NOPREPARE);
                error = simplecmd(xc, c);
                assert(error == 0);
                freecmd(c);
                c = createcmd("SET SESSION CHARACTERISTICS AS "
                    "TRANSACTION ISOLATION LEVEL REPEATABLE READ",
                    CMD_NOPREPARE);
                error = simplecmd(xc, c);
                assert(error == 0);
                freecmd(c);
                c = createcmd("SET SESSION TIME ZONE UTC", CMD_NOPREPARE);
                error = simplecmd(xc, c);
                assert(error == 0);
                freecmd(c);
                if (!pgfs_dosync) {
                        c = createcmd("SET SESSION SYNCHRONOUS_COMMIT TO OFF",
                            CMD_NOPREPARE);
                        error = simplecmd(xc, c);
                        assert(error == 0);
                        freecmd(c);
                }
                if (debug) {
                        struct fetchstatus s;
                        static const Oid types[] = { INT8OID, };
                        uint64_t pid;

                        c = createcmd("SELECT pg_backend_pid()::int8;",
                            CMD_NOPREPARE);
                        error = sendcmd(xc, c);
                        assert(error == 0);
                        fetchinit(&s, xc);
                        error = FETCHNEXT(&s, types, &pid);
                        fetchdone(&s);
                        assert(error == 0);
                        DPRINTF("xc %p backend pid %" PRIu64 "\n", xc, pid);
                }
                error = commit(xc);
                assert(error == 0);
                assert(xc->owner == NULL);
        }
        /*
         * XXX cleanup unlinked files here?  what to do when the filesystem
         * is shared?
         */
        return 0;
}

struct waitq flushwaitq = TAILQ_HEAD_INITIALIZER(flushwaitq);
struct puffs_cc *flusher = NULL;

int
flush_xacts(struct puffs_usermount *pu)
{
        struct puffs_cc *cc = puffs_cc_getcc(pu);
        struct Xconn *xc;
        static struct cmd *c;
        uint64_t dummy;
        int error;

        /*
         * flush all previously issued asynchronous transactions.
         *
         * XXX
         * unfortunately it seems that there is no clean way to tell
         * PostgreSQL flush XLOG.  we could perform a CHECKPOINT but it's
         * too expensive and overkill for our purpose.
         * besides, PostgreSQL has an optimization to skip XLOG flushing
         * for transactions which didn't produce WAL records.
         * (changeset f6a0863e3cb72763490ceca2c558d5ef2dddd5f2)
         * it means that an empty transaction ("BEGIN; COMMIT;"), which
         * doesn't produce any WAL records, doesn't flush the XLOG even if
         * synchronous_commit=on.  we issues a dummy setval() to avoid the
         * optimization.
         * on the other hand, we try to avoid creating unnecessary WAL activity
         * by serializing flushing and checking XLOG locations.
         */

        assert(!pgfs_dosync);
        if (flusher != NULL) { /* serialize flushers */
                DPRINTF("%p flush in progress %p\n", cc, flusher);
                waiton(&flushwaitq, cc);
                assert(flusher == NULL);
        }
        DPRINTF("%p start flushing\n", cc);
        flusher = cc;
retry:
        xc = begin(pu, "flush");
        CREATECMD_NOPARAM(c, "SELECT setval('dummyseq', 1) WHERE "
            "pg_current_xlog_insert_location() <> pg_current_xlog_location()");
        error = sendcmd(xc, c);
        if (error != 0) {
                goto got_error;
        }
        error = simplefetch(xc, INT8OID, &dummy);
        assert(error != 0 || dummy == 1);
        if (error == ENOENT) {
                /*
                 * there seems to be nothing to flush.
                 */
                DPRINTF("%p no sync\n", cc);
                error = 0;
        }
        if (error != 0) {
                goto got_error;
        }
        error = commit_sync(xc);
        if (error != 0) {
                goto got_error;
        }
        goto done;
got_error:
        rollback(xc);
        if (error == EAGAIN) {
                goto retry;
        }
done:
        assert(flusher == cc);
        flusher = NULL;
        wakeup_one(&flushwaitq);
        DPRINTF("%p end flushing error=%d\n", cc, error);
        return error;
}