mariadb/ft/txn_manager.c

/* -*- mode: C; c-basic-offset: 4; indent-tabs-mode: nil -*- */
// vim: expandtab:ts=8:sw=4:softtabstop=4:
#ident "$Id$"
#ident "Copyright (c) 2007-2010 Tokutek Inc.  All rights reserved."
#ident "The technology is licensed by the Massachusetts Institute of Technology, Rutgers State University of New Jersey, and the Research Foundation of State University of New York at Stony Brook under United States of America Serial No. 11/760379 and to the patents and/or patent applications resulting from it."


#include "includes.h"
#include "txn.h"
#include "checkpoint.h"
#include "ule.h"
#include <valgrind/helgrind.h>
#include "txn_manager.h"

struct txn_manager {
    toku_mutex_t txn_manager_lock;  // a lock protecting live_list_reverse and snapshot_txnids for now TODO: revisit this decision
    OMT live_txns; // a sorted tree.  Old comment said should be a hashtable.  Do we still want that?
    OMT live_root_txns; // a sorted tree.
    OMT snapshot_txnids;    //contains TXNID x | x is snapshot txn
    //contains TXNID pairs (x,y) | y is oldest txnid s.t. x is in y's live list
    // every TXNID that is in some snapshot's live list is used as the key for this OMT, x, as described above. 
    // The second half of the pair, y, is the youngest snapshot txnid (that is, has the highest LSN), such that x is in its live list.
    // So, for example, Say T_800 begins, T_800 commits right after snapshot txn T_1100  begins. Then (800,1100) is in 
    // this list
    OMT live_list_reverse;  
    TXNID oldest_living_xid;
    time_t oldest_living_starttime;   // timestamp in seconds of when txn with oldest_living_xid started
    struct toku_list prepared_txns; // transactions that have been prepared and are unresolved, but have not been returned through txn_recover.
    struct toku_list prepared_and_returned_txns; // transactions that have been prepared and unresolved, and have been returned through txn_recover.  We need this list so that we can restart the recovery.

    toku_cond_t wait_for_unpin_of_txn;
};

static TXN_MANAGER_STATUS_S txn_manager_status;
BOOL garbage_collection_debug = FALSE;


#define STATUS_INIT(k,t,l) { \
    txn_manager_status.status[k].keyname = #k; \
    txn_manager_status.status[k].type    = t;  \
    txn_manager_status.status[k].legend  = "txn: " l; \
    }

static void
status_init(void) {
    // Note, this function initializes the keyname, type, and legend fields.
    // Value fields are initialized to zero by compiler.
    STATUS_INIT(TXN_OLDEST_LIVE,      UINT64,   "xid of oldest live transaction");
    STATUS_INIT(TXN_OLDEST_STARTTIME, UNIXTIME, "start time of oldest live transaction");
    txn_manager_status.initialized = true;
}
#undef STATUS_INIT

#define STATUS_VALUE(x) txn_manager_status.status[x].value.num

static BOOL is_txnid_live(TXN_MANAGER txn_manager, TXNID txnid) {
    TOKUTXN result = NULL;
    toku_txn_manager_id2txn_unlocked(txn_manager, txnid, &result);
    return (result != NULL);
}

static void
verify_snapshot_system(TXN_MANAGER txn_manager) {
    int     num_snapshot_txnids = toku_omt_size(txn_manager->snapshot_txnids);
    TXNID       snapshot_txnids[num_snapshot_txnids];
    int     num_live_txns = toku_omt_size(txn_manager->live_txns);
    TOKUTXN     live_txns[num_live_txns];
    int     num_live_list_reverse = toku_omt_size(txn_manager->live_list_reverse);
    XID_PAIR    live_list_reverse[num_live_list_reverse];

    int r;
    int i;
    int j;
    //set up arrays for easier access
    for (i = 0; i < num_snapshot_txnids; i++) {
        OMTVALUE v;
        r = toku_omt_fetch(txn_manager->snapshot_txnids, i, &v);
        assert_zero(r);
        snapshot_txnids[i] = (TXNID) v;
    }
    for (i = 0; i < num_live_txns; i++) {
        OMTVALUE v;
        r = toku_omt_fetch(txn_manager->live_txns, i, &v);
        assert_zero(r);
        live_txns[i] = v;
    }
    for (i = 0; i < num_live_list_reverse; i++) {
        OMTVALUE v;
        r = toku_omt_fetch(txn_manager->live_list_reverse, i, &v);
        assert_zero(r);
        live_list_reverse[i] = v;
    }

    {
        //Verify snapshot_txnids
        for (i = 0; i < num_snapshot_txnids; i++) {
            TXNID snapshot_xid = snapshot_txnids[i];
            invariant(is_txnid_live(txn_manager, snapshot_xid));
            TOKUTXN snapshot_txn;
            toku_txn_manager_id2txn_unlocked(txn_manager, snapshot_xid, &snapshot_txn);
            int   num_live_root_txn_list = toku_omt_size(snapshot_txn->live_root_txn_list);
            TXNID     live_root_txn_list[num_live_root_txn_list];
            {
                for (j = 0; j < num_live_root_txn_list; j++) {
                    OMTVALUE v;
                    r = toku_omt_fetch(snapshot_txn->live_root_txn_list, j, &v);
                    assert_zero(r);
                    live_root_txn_list[j] = (TXNID)v;
                }
            }
            for (j = 0; j < num_live_root_txn_list; j++) {
                TXNID live_xid = live_root_txn_list[j];
                invariant(live_xid <= snapshot_xid);
                TXNID youngest = toku_get_youngest_live_list_txnid_for(
                    live_xid, 
                    txn_manager->live_list_reverse
                    );
                invariant(youngest!=TXNID_NONE);
                invariant(youngest>=snapshot_xid);
            }
        }
    }
    {
        //Verify live_list_reverse
        for (i = 0; i < num_live_list_reverse; i++) {
            XID_PAIR pair = live_list_reverse[i];
            invariant(pair->xid1 <= pair->xid2);

            {
                //verify pair->xid2 is in snapshot_xids
                u_int32_t index;
                OMTVALUE v2;
                r = toku_omt_find_zero(txn_manager->snapshot_txnids,
                                       toku_find_xid_by_xid,
                                       (OMTVALUE) pair->xid2, &v2, &index);
                assert_zero(r);
            }
            for (j = 0; j < num_live_txns; j++) {
                TOKUTXN txn = live_txns[j];
                if (txn->snapshot_type != TXN_SNAPSHOT_NONE) {
                    BOOL expect = txn->snapshot_txnid64 >= pair->xid1 &&
                                  txn->snapshot_txnid64 <= pair->xid2;
                    BOOL found = toku_is_txn_in_live_root_txn_list(txn->live_root_txn_list, pair->xid1);
                    invariant((expect==FALSE) == (found==FALSE));
                }
            }
        }
    }
    {
        //Verify live_txns
        for (i = 0; i < num_live_txns; i++) {
            TOKUTXN txn = live_txns[i];

            BOOL expect = txn->snapshot_txnid64 == txn->txnid64;
            {
                //verify pair->xid2 is in snapshot_xids
                u_int32_t index;
                OMTVALUE v2;
                r = toku_omt_find_zero(txn_manager->snapshot_txnids,
                                       toku_find_xid_by_xid,
                                       (OMTVALUE) txn->txnid64, &v2, &index);
                invariant(r==0 || r==DB_NOTFOUND);
                invariant((r==0) == (expect!=0));
            }

        }
    }
}

static TXNID txn_manager_get_oldest_living_xid_unlocked(
    TXN_MANAGER txn_manager, 
    time_t * oldest_living_starttime
    );

void toku_txn_manager_get_status(TOKULOGGER logger, TXN_MANAGER_STATUS s) {
    if (!txn_manager_status.initialized) {
        status_init();
    }
    {
        if (logger) {
            time_t oldest_starttime;
            STATUS_VALUE(TXN_OLDEST_LIVE) = txn_manager_get_oldest_living_xid_unlocked(logger->txn_manager, &oldest_starttime);
            STATUS_VALUE(TXN_OLDEST_STARTTIME) = (uint64_t) oldest_starttime;
        }
    }
    *s = txn_manager_status;
}


void toku_txn_manager_init(TXN_MANAGER* txn_managerp) {
    int r = 0;
    TXN_MANAGER XMALLOC(txn_manager);
    toku_mutex_init(&txn_manager->txn_manager_lock, NULL);
    r = toku_omt_create(&txn_manager->live_txns); 
    assert_zero(r);
    r = toku_omt_create(&txn_manager->live_root_txns);
    assert_zero(r);
    r = toku_omt_create(&txn_manager->snapshot_txnids);
    assert_zero(r);
    r = toku_omt_create(&txn_manager->live_list_reverse);
    assert_zero(r);
    txn_manager->oldest_living_xid = TXNID_NONE_LIVING;
    txn_manager->oldest_living_starttime = 0;
    toku_list_init(&txn_manager->prepared_txns);
    toku_list_init(&txn_manager->prepared_and_returned_txns);

    toku_cond_init(&txn_manager->wait_for_unpin_of_txn, 0);
    *txn_managerp = txn_manager;
}

void toku_txn_manager_destroy(TXN_MANAGER txn_manager) {
    toku_mutex_destroy(&txn_manager->txn_manager_lock);
    toku_omt_destroy(&txn_manager->live_txns);
    toku_omt_destroy(&txn_manager->live_root_txns);
    toku_omt_destroy(&txn_manager->snapshot_txnids);
    toku_omt_destroy(&txn_manager->live_list_reverse);
    toku_cond_destroy(&txn_manager->wait_for_unpin_of_txn);
    toku_free(txn_manager);
}

static TXNID txn_manager_get_oldest_living_xid_unlocked(
    TXN_MANAGER txn_manager, 
    time_t * oldest_living_starttime
    ) 
{
    TXNID rval = 0;
    rval = txn_manager->oldest_living_xid;
    if (oldest_living_starttime) {
        *oldest_living_starttime = txn_manager->oldest_living_starttime;
    }
    return rval;
}

TXNID toku_txn_manager_get_oldest_living_xid(TXN_MANAGER txn_manager, time_t * oldest_living_starttime) {
    TXNID rval = 0;
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    rval = txn_manager_get_oldest_living_xid_unlocked(txn_manager, oldest_living_starttime);    
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
    return rval;
}

// Create list of root transactions that were live when this txn began.
static int
setup_live_root_txn_list(TXN_MANAGER txn_manager, TOKUTXN txn) {
    OMT global = txn_manager->live_root_txns;
    int r = toku_omt_clone_noptr(
        &txn->live_root_txn_list,
        global
        );
    return r;
}

// Add this txn to the global list of txns that have their own snapshots.
// (Note, if a txn is a child that creates its own snapshot, then that child xid
// is the xid stored in the global list.) 
static int
snapshot_txnids_note_txn(TXN_MANAGER txn_manager, TOKUTXN txn) {
    int r;
    OMT txnids = txn_manager->snapshot_txnids;
    r = toku_omt_insert_at(txnids, (OMTVALUE) txn->txnid64, toku_omt_size(txnids));
    assert_zero(r);
    return r;
}

// If live txn is not in reverse live list, then add it.
// If live txn is in reverse live list, update it by setting second xid in pair to new txn that is being started.
static int
live_list_reverse_note_txn_start_iter(OMTVALUE live_xidv, u_int32_t UU(index), void*txnv) {
    TOKUTXN txn = txnv;
    TXNID xid   = txn->txnid64;     // xid of new txn that is being started
    TXNID live_xid = (TXNID)live_xidv;    // xid on the new txn's live list
    OMTVALUE pairv;
    XID_PAIR pair;
    uint32_t idx;

    int r;
    OMT reverse = txn->logger->txn_manager->live_list_reverse;
    r = toku_omt_find_zero(reverse, toku_find_pair_by_xid, (void *)live_xid, &pairv, &idx);
    if (r==0) {
        pair = pairv;
        invariant(pair->xid1 == live_xid); //sanity check
        invariant(pair->xid2 < xid);        //Must be older
        pair->xid2 = txn->txnid64;
    }
    else {
        invariant(r==DB_NOTFOUND);
        //Make new entry
        XMALLOC(pair);
        pair->xid1 = live_xid;
        pair->xid2 = txn->txnid64;
        r = toku_omt_insert_at(reverse, pair, idx);
        assert_zero(r);
    }
    return r;
}

// Maintain the reverse live list.  The reverse live list is a list of xid pairs.  The first xid in the pair
// is a txn that was live when some txn began, and the second xid in the pair is the newest still-live xid to 
// have that first xid in its live list.  (The first xid may be closed, it only needed to be live when the 
// second txn began.)
// When a new txn begins, we need to scan the live list of this new txn.  For each live txn, we either 
// add it to the reverse live list (if it is not already there), or update to the reverse live list so
// that this new txn is the second xid in the pair associated with the txn in the live list.
static int
live_list_reverse_note_txn_start(TOKUTXN txn) {
    int r;

    r = toku_omt_iterate(txn->live_root_txn_list, live_list_reverse_note_txn_start_iter, txn);
    assert_zero(r);
    return r;
}

int toku_txn_manager_start_txn(
    TOKUTXN *txnp,
    TXN_MANAGER txn_manager,
    TOKUTXN parent,
    TOKULOGGER logger,
    TXNID xid,
    TXN_SNAPSHOT_TYPE snapshot_type,
    DB_TXN *container_db_txn,
    bool for_recovery)
{
    int r;
    // we take the txn_manager_lock before writing to the log
    // we may be able to move this lock acquisition
    // down to just before inserting into logger->live_txns
    // if we know the caller has the multi operation lock
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    if (garbage_collection_debug) {
        verify_snapshot_system(txn_manager);
    }
    if (xid == TXNID_NONE) {
        LSN first_lsn;
        r = toku_log_xbegin(logger, &first_lsn, 0, parent ? parent->txnid64 : 0);
        assert_zero(r);
        xid = first_lsn.lsn;
    } 
    XIDS parent_xids;
    if (parent == NULL)
        parent_xids = xids_get_root_xids();
    else
        parent_xids = parent->xids;
    XIDS xids;
    r = xids_create_child(parent_xids, &xids, xid);
    assert_zero(r);

    TOKUTXN txn;
    r = toku_txn_create_txn(&txn, parent, logger, xid, snapshot_type, xids, container_db_txn, for_recovery);
    if (r != 0) {
        // logger is panicked
        return r;
    }

    if (toku_omt_size(txn_manager->live_txns) == 0) {
        assert(txn_manager->oldest_living_xid == TXNID_NONE_LIVING);
        txn_manager->oldest_living_xid = txn->txnid64;
        txn_manager->oldest_living_starttime = txn->starttime;
    }
    assert(txn_manager->oldest_living_xid <= txn->txnid64);

    {
        //Add txn to list (omt) of live transactions
        //We know it is the newest one.
        r = toku_omt_insert_at(txn_manager->live_txns, txn, toku_omt_size(txn_manager->live_txns));
        assert_zero(r);

        //
        // maintain the data structures necessary for MVCC:
        //  1. add txn to list of live_root_txns if this is a root transaction
        //  2. if the transaction is creating a snapshot:
        //    - create a live list for the transaction
        //    - add the id to the list of snapshot ids
        //    - make the necessary modifications to the live_list_reverse
        //
        // The order of operations is important here, and must be taken
        // into account when the transaction is closed. The txn is added
        // to the live_root_txns first (if it is a root txn). This has the implication
        // that a root level snapshot transaction is in its own live list. This fact
        // is taken into account when the transaction is closed.
        //

        // add ancestor information, and maintain global live root txn list
        if (parent == NULL) {
            //Add txn to list (omt) of live root txns
            r = toku_omt_insert_at(
                txn_manager->live_root_txns, 
                (OMTVALUE) txn->txnid64, 
                toku_omt_size(txn_manager->live_root_txns)
                ); //We know it is the newest one.
            assert_zero(r);
        }

        // setup information for snapshot reads
        if (txn->snapshot_type != TXN_SNAPSHOT_NONE) {
            // in this case, either this is a root level transaction that needs its live list setup, or it
            // is a child transaction that specifically asked for its own snapshot
            if (parent == NULL || txn->snapshot_type == TXN_SNAPSHOT_CHILD) {
                r = setup_live_root_txn_list(txn_manager, txn);  
                assert_zero(r);
                r = snapshot_txnids_note_txn(txn_manager, txn);
                assert_zero(r);
                r = live_list_reverse_note_txn_start(txn);
                assert_zero(r);
            }
            // in this case, it is a child transaction that specified its snapshot to be that 
            // of the root transaction
            else if (txn->snapshot_type == TXN_SNAPSHOT_ROOT) {
                txn->live_root_txn_list = parent->live_root_txn_list;
            }
            else {
                assert(FALSE);
            }
        }
    }
    if (garbage_collection_debug) {
        verify_snapshot_system(txn_manager);
    }
    toku_mutex_unlock(&txn_manager->txn_manager_lock);

    *txnp = txn;
    return 0;
}

// For each xid on the closing txn's live list, find the corresponding entry in the reverse live list.
// There must be one.
// If the second xid in the pair is not the xid of the closing transaction, then the second xid must be newer
// than the closing txn, and there is nothing to be done (except to assert the invariant).
// If the second xid in the pair is the xid of the closing transaction, then we need to find the next oldest
// txn.  If the live_xid is in the live list of the next oldest txn, then set the next oldest txn as the 
// second xid in the pair, otherwise delete the entry from the reverse live list.
static int
live_list_reverse_note_txn_end_iter(OMTVALUE live_xidv, u_int32_t UU(index), void*txnv) {
    TOKUTXN txn = txnv;
    TXNID xid = txn->txnid64;          // xid of txn that is closing
    TXNID live_xid = (TXNID)live_xidv;       // xid on closing txn's live list
    OMTVALUE pairv;
    XID_PAIR pair;
    uint32_t idx;

    int r;
    OMT reverse = txn->logger->txn_manager->live_list_reverse;
    r = toku_omt_find_zero(reverse, toku_find_pair_by_xid, (void *)live_xid, &pairv, &idx);
    invariant(r==0);
    pair = pairv;
    invariant(pair->xid1 == live_xid); //sanity check
    if (pair->xid2 == xid) {
        //There is a record that needs to be either deleted or updated
        TXNID olderxid;
        OMTVALUE olderv;
        uint32_t olderidx;
        OMT snapshot = txn->logger->txn_manager->snapshot_txnids;
        BOOL should_delete = TRUE;
        // find the youngest txn in snapshot that is older than xid
        r = toku_omt_find(snapshot, toku_find_xid_by_xid, (OMTVALUE) xid, -1, &olderv, &olderidx);
        if (r==0) {
            //There is an older txn
            olderxid = (TXNID) olderv;
            invariant(olderxid < xid);
            if (olderxid >= live_xid) {
                //older txn is new enough, we need to update.
                pair->xid2 = olderxid;
                should_delete = FALSE;
            }
        }
        else {
            invariant(r==DB_NOTFOUND);
        }
        if (should_delete) {
            //Delete record
            toku_free(pair);
            r = toku_omt_delete_at(reverse, idx);
            invariant(r==0);
        }
    }
    else {
        invariant(pair->xid2 > xid);
    }
    return r;
}

// When txn ends, update reverse live list.  To do that, examine each txn in this (closing) txn's live list.
static int
live_list_reverse_note_txn_end(TOKUTXN txn) {
    int r;

    r = toku_omt_iterate(txn->live_root_txn_list, live_list_reverse_note_txn_end_iter, txn);
    invariant(r==0);
    return r;
}

//Heaviside function to find a TOKUTXN by TOKUTXN (used to find the index)
static int find_xid (OMTVALUE v, void *txnv) {
    TOKUTXN txn = v;
    TOKUTXN txnfind = txnv;
    if (txn->txnid64<txnfind->txnid64) return -1;
    if (txn->txnid64>txnfind->txnid64) return +1;
    return 0;
}

void toku_txn_manager_finish_txn(TXN_MANAGER txn_manager, TOKUTXN txn) {
    int r;
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    {
        if (garbage_collection_debug) {
            verify_snapshot_system(txn_manager);
        }
        {
            //Remove txn from list (omt) of live transactions
            OMTVALUE txnagain;
            u_int32_t idx;
            r = toku_omt_find_zero(txn_manager->live_txns, find_xid, txn, &txnagain, &idx);
            assert(r==0);
            assert(txn==txnagain);
            r = toku_omt_delete_at(txn_manager->live_txns, idx);
            assert(r==0);
        }

        if (txn->parent==NULL) {
            OMTVALUE v;
            u_int32_t idx;
            //Remove txn from list of live root txns
            r = toku_omt_find_zero(txn_manager->live_root_txns, toku_find_xid_by_xid, (OMTVALUE)txn->txnid64, &v, &idx);
            assert(r==0);
            TXNID xid = (TXNID) v;
            invariant(xid == txn->txnid64);
            r = toku_omt_delete_at(txn_manager->live_root_txns, idx);
            assert(r==0);
        }
        //
        // if this txn created a snapshot, make necessary modifications to list of snapshot txnids and live_list_reverse
        // the order of operations is important. We first remove the txnid from the list of snapshot txnids. This is
        // necessary because root snapshot transactions are in their own live lists. If we do not remove 
        // the txnid from the snapshot txnid list first, then when we go to make the modifications to 
        // live_list_reverse, we have trouble. We end up never removing (id, id) from live_list_reverse
        //
        if (txn->snapshot_type != TXN_SNAPSHOT_NONE && (txn->parent==NULL || txn->snapshot_type == TXN_SNAPSHOT_CHILD)) {
            {
                u_int32_t idx;
                OMTVALUE v;
                //Free memory used for snapshot_txnids
                r = toku_omt_find_zero(txn_manager->snapshot_txnids, toku_find_xid_by_xid, (OMTVALUE) txn->txnid64, &v, &idx);
                invariant(r==0);
                TXNID xid = (TXNID) v;
                invariant(xid == txn->txnid64);
                r = toku_omt_delete_at(txn_manager->snapshot_txnids, idx);
                invariant(r==0);
            }
            live_list_reverse_note_txn_end(txn);
            {
                //Free memory used for live root txns local list
                invariant(toku_omt_size(txn->live_root_txn_list) > 0);
                toku_omt_destroy(&txn->live_root_txn_list);
            }
        }
    }

    assert(txn_manager->oldest_living_xid <= txn->txnid64);
    if (txn->txnid64 == txn_manager->oldest_living_xid) {
        OMTVALUE oldest_txnv;
        r = toku_omt_fetch(txn_manager->live_txns, 0, &oldest_txnv);
        if (r==0) {
            TOKUTXN oldest_txn = oldest_txnv;
            assert(oldest_txn != txn); // We just removed it
            assert(oldest_txn->txnid64 > txn_manager->oldest_living_xid); //Must be newer than the previous oldest
            txn_manager->oldest_living_xid = oldest_txn->txnid64;
            txn_manager->oldest_living_starttime = oldest_txn->starttime;
        }
        else {
            //No living transactions
            assert(r==EINVAL);
            txn_manager->oldest_living_xid = TXNID_NONE_LIVING;
            txn_manager->oldest_living_starttime = 0;
        }
    }
    if (garbage_collection_debug) {
        verify_snapshot_system(txn_manager);
    }
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
}

void toku_txn_manager_clone_state_for_gc(
    TXN_MANAGER txn_manager, 
    OMT* snapshot_xids, 
    OMT* live_list_reverse, 
    OMT* live_root_txns
    ) 
{
    int r = 0;
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    r = toku_omt_clone_noptr(snapshot_xids,
                             txn_manager->snapshot_txnids);
    assert_zero(r);
    r = toku_omt_clone_pool(live_list_reverse,
                            txn_manager->live_list_reverse,
                            sizeof(XID_PAIR_S));
    assert_zero(r);
    r = toku_omt_clone_noptr(live_root_txns,
                             txn_manager->live_root_txns);
    assert_zero(r);
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
}

//Heaviside function to search through an OMT by a TXNID
static int
find_by_xid (OMTVALUE v, void *txnidv) {
    TOKUTXN txn = v;
    TXNID   txnidfind = *(TXNID*)txnidv;
    if (txn->txnid64<txnidfind) return -1;
    if (txn->txnid64>txnidfind) return +1;
    return 0;
}

void toku_txn_manager_id2txn_unlocked(TXN_MANAGER txn_manager, TXNID txnid, TOKUTXN *result) {
    OMTVALUE txnfound;
    int r = toku_omt_find_zero(txn_manager->live_txns, find_by_xid, &txnid, &txnfound, NULL);
    if (r==0) {
        TOKUTXN txn = txnfound;
        assert(txn->txnid64==txnid);
        *result = txn;
    }
    else {
        assert(r==DB_NOTFOUND);
        // If there is no txn, then we treat it as the null txn.
        *result = NULL;
    }
}

void toku_txn_manager_id2txn(TXN_MANAGER txn_manager, TXNID txnid, TOKUTXN *result) {
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    toku_txn_manager_id2txn_unlocked(txn_manager, txnid, result);
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
}

int toku_txn_manager_get_txn_from_xid (TXN_MANAGER txn_manager, TOKU_XA_XID *xid, DB_TXN **txnp) {
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    int ret_val = 0;
    int num_live_txns = toku_omt_size(txn_manager->live_txns);
    for (int i = 0; i < num_live_txns; i++) {
        OMTVALUE v;
        {
            int r = toku_omt_fetch(txn_manager->live_txns, i, &v);
            assert_zero(r);
        }
        TOKUTXN txn = v;
        if (txn->xa_xid.formatID     == xid->formatID
            && txn->xa_xid.gtrid_length == xid->gtrid_length
            && txn->xa_xid.bqual_length == xid->bqual_length
            && 0==memcmp(txn->xa_xid.data, xid->data, xid->gtrid_length + xid->bqual_length)) {
            *txnp = txn->container_db_txn;
            ret_val = 0;
            goto exit;
        }
    }
    ret_val = DB_NOTFOUND;
exit:
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
    return ret_val;
}

u_int32_t toku_txn_manager_num_live_txns(TXN_MANAGER txn_manager) {
    int ret_val = 0;
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    ret_val = toku_omt_size(txn_manager->live_txns);
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
    return ret_val;
}

int toku_txn_manager_iter_over_live_txns(
    TXN_MANAGER txn_manager, 
    int (*f)(OMTVALUE, u_int32_t, void*), 
    void* v
    ) 
{
    int r = 0;
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    r = toku_omt_iterate(txn_manager->live_txns, f, v);
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
    return r;
}

void toku_txn_manager_add_prepared_txn(TXN_MANAGER txn_manager, TOKUTXN txn) {
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    assert(txn->state==TOKUTXN_LIVE);
    txn->state = TOKUTXN_PREPARING; // This state transition must be protected against begin_checkpoint.  Right now it uses the ydb lock.
    toku_list_push(&txn_manager->prepared_txns, &txn->prepared_txns_link);
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
}

static void invalidate_xa_xid (TOKU_XA_XID *xid) {
    ANNOTATE_NEW_MEMORY(xid, sizeof(*xid)); // consider it to be all invalid for valgrind
    xid->formatID = -1; // According to the XA spec, -1 means "invalid data"
}

void toku_txn_manager_note_abort_txn(TXN_MANAGER txn_manager, TOKUTXN txn) {
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    if (txn->state==TOKUTXN_PREPARING) {
        invalidate_xa_xid(&txn->xa_xid);
        toku_list_remove(&txn->prepared_txns_link);
    }
    // for hot indexing, if hot index is processing
    // this transaction in some leafentry, then we cannot change
    // the state to commit or abort until
    // hot index is done with that leafentry
    while (txn->num_pin > 0) {
        toku_cond_wait(
            &txn_manager->wait_for_unpin_of_txn, 
            &txn_manager->txn_manager_lock
            );
    }
    txn->state = TOKUTXN_ABORTING;
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
}

void toku_txn_manager_note_commit_txn(TXN_MANAGER txn_manager, TOKUTXN txn) {
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    if (txn->state==TOKUTXN_PREPARING) {
        invalidate_xa_xid(&txn->xa_xid);
        toku_list_remove(&txn->prepared_txns_link);
    }
    // for hot indexing, if hot index is processing
    // this transaction in some leafentry, then we cannot change
    // the state to commit or abort until
    // hot index is done with that leafentry
    while (txn->num_pin > 0) {
        toku_cond_wait(
            &txn_manager->wait_for_unpin_of_txn, 
            &txn_manager->txn_manager_lock
            );
    }
    txn->state = TOKUTXN_COMMITTING;
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
}

int toku_txn_manager_recover_txn (
    TXN_MANAGER txn_manager, 
    struct tokulogger_preplist preplist[/*count*/], 
    long count, 
    long *retp, /*out*/ 
    u_int32_t flags
    )
{
    int ret_val = 0;
    toku_mutex_lock(&txn_manager->txn_manager_lock);
    if (flags==DB_FIRST) {
        // Anything in the returned list goes back on the prepared list.
        while (!toku_list_empty(&txn_manager->prepared_and_returned_txns)) {
            struct toku_list *h = toku_list_head(&txn_manager->prepared_and_returned_txns);
            toku_list_remove(h);
            toku_list_push(&txn_manager->prepared_txns, h);
        }
    } else if (flags!=DB_NEXT) { 
        ret_val = EINVAL;
        goto exit;
    }
    long i;
    for (i=0; i<count; i++) {
        if (!toku_list_empty(&txn_manager->prepared_txns)) {
            struct toku_list *h = toku_list_head(&txn_manager->prepared_txns);
            toku_list_remove(h);
            toku_list_push(&txn_manager->prepared_and_returned_txns, h);
            TOKUTXN txn = toku_list_struct(h, struct tokutxn, prepared_txns_link);
            assert(txn->container_db_txn);
            preplist[i].txn = txn->container_db_txn;
            preplist[i].xid = txn->xa_xid;
        } else {
            break;
        }
    }
    *retp = i;
    ret_val = 0;
exit:
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
    return ret_val;
}

// needed for hot indexing
void toku_txn_manager_pin_live_txn_unlocked(TXN_MANAGER UU(txn_manager), TOKUTXN txn) {
    assert(txn->state == TOKUTXN_LIVE || txn->state == TOKUTXN_PREPARING);
    txn->num_pin++;
}

void toku_txn_manager_unpin_live_txn_unlocked(TXN_MANAGER txn_manager, TOKUTXN txn) {
    assert(txn->state == TOKUTXN_LIVE || txn->state == TOKUTXN_PREPARING);
    assert(txn->num_pin > 0);
    txn->num_pin--;
    if (txn->num_pin == 0) {
        toku_cond_broadcast(&txn_manager->wait_for_unpin_of_txn);
    }
}

void toku_txn_manager_suspend(TXN_MANAGER txn_manager) {
    toku_mutex_lock(&txn_manager->txn_manager_lock);    
}
void toku_txn_manager_resume(TXN_MANAGER txn_manager) {
    toku_mutex_unlock(&txn_manager->txn_manager_lock);
}


#undef STATUS_VALUE