src/lib-index/mail-index-transaction.c

	mail-index-transaction.c revision 27bc15088a485a8047fca9b0d24d2904c6dda919
bcb4e51a409d94ae670de96afb8483a4f7855294Stephan Bosch/* Copyright (C) 2003-2004 Timo Sirainen */
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi/* Inside transaction we keep messages stored in sequences in uid fields.
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi   Before they're written to transaction log the sequences are changed to
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi   UIDs. This is because we're able to compress sequence ranges better. */
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "lib.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "ioloop.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "array.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "bsearch-insert-pos.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "seq-range-array.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "mail-index-view-private.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "mail-transaction-log.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "mail-cache-private.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include "mail-index-transaction-private.h"
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include <stddef.h>
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include <stdlib.h>
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi#include <time.h>
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomivoid (*hook_mail_index_transaction_created)
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        (struct mail_index_transaction *t) = NULL;
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomivoid mail_index_transaction_reset(struct mail_index_transaction *t)
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi{
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    ARRAY_TYPE(seq_array) *recs;
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    struct mail_index_transaction_ext_hdr_update **ext_hdrs;
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    unsigned i, count;
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->ext_rec_updates)) {
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        recs = array_get_modifiable(&t->ext_rec_updates, &count);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        for (i = 0; i < count; i++) {
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi            if (array_is_created(&recs[i]))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi                array_free(&recs[i]);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        }
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->ext_rec_updates);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    }
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->ext_hdr_updates)) {
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        ext_hdrs = array_get_modifiable(&t->ext_hdr_updates, &count);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        for (i = 0; i < count; i++)
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi            i_free(ext_hdrs[i]);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->ext_hdr_updates);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    }
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->keyword_updates)) {
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        struct mail_index_transaction_keyword_update *u;
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        u = array_get_modifiable(&t->keyword_updates, &count);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        for (i = 0; i < count; i++) {
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi            if (array_is_created(&u[i].add_seq))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi                array_free(&u[i].add_seq);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi            if (array_is_created(&u[i].remove_seq))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi                array_free(&u[i].remove_seq);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        }
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->keyword_updates);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    }
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->keyword_resets))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->keyword_resets);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->appends))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->appends);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->expunges))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->expunges);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->updates))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->updates);
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi    if (array_is_created(&t->ext_resizes))
e88e76e782853e826d00524ee1133e64fb69b3d9Aki Tuomi        array_free(&t->ext_resizes);
    if (array_is_created(&t->ext_resets))
        array_free(&t->ext_resets);

    t->first_new_seq = mail_index_view_get_messages_count(t->view)+1;
    t->last_new_seq = 0;
    t->last_update_idx = 0;

    memset(t->pre_hdr_mask, 0, sizeof(t->pre_hdr_mask));
    memset(t->post_hdr_mask, 0, sizeof(t->post_hdr_mask));

    if (t->cache_trans_ctx != NULL) {
        mail_cache_transaction_rollback(t->cache_trans_ctx);
                t->cache_trans_ctx = NULL;
    }

    t->appends_nonsorted = FALSE;
    t->pre_hdr_changed = FALSE;
    t->post_hdr_changed = FALSE;
    t->reset = FALSE;
    t->log_updates = FALSE;
    t->log_ext_updates = FALSE;
}

static void mail_index_transaction_free(struct mail_index_transaction *t)
{
    mail_index_transaction_reset(t);

    array_free(&t->module_contexts);
    mail_index_view_transaction_unref(t->view);
    mail_index_view_close(&t->view);
    i_free(t);
}

struct mail_index_view *
mail_index_transaction_get_view(struct mail_index_transaction *t)
{
    return t->view;
}

bool mail_index_transaction_is_expunged(struct mail_index_transaction *t,
                    uint32_t seq)
{
    return array_is_created(&t->expunges) &&
        seq_range_exists(&t->expunges, seq);
}

void mail_index_transaction_ref(struct mail_index_transaction *t)
{
    t->refcount++;
}

void mail_index_transaction_unref(struct mail_index_transaction **_t)
{
    struct mail_index_transaction *t = *_t;

    *_t = NULL;
    if (--t->refcount == 0)
        mail_index_transaction_free(t);
}

static int mail_index_seq_record_cmp(const void *key, const void *data)
{
    const uint32_t *seq_p = key;
    const uint32_t *data_seq = data;

    return *seq_p - *data_seq;
}

bool mail_index_seq_array_lookup(const ARRAY_TYPE(seq_array) *array,
                 uint32_t seq, unsigned int *idx_r)
{
    const void *base;
    unsigned int count;

    base = array_get(array, &count);
    return bsearch_insert_pos(&seq, base, count, array->arr.element_size,
                  mail_index_seq_record_cmp, idx_r);
}

static bool mail_index_seq_array_add(ARRAY_TYPE(seq_array) *array, uint32_t seq,
                     const void *record, size_t record_size,
                     void *old_record)
{
    void *p;
    unsigned int idx, aligned_record_size;

    /* records need to be 32bit aligned */
    aligned_record_size = (record_size + 3) & ~3;

    if (!array_is_created(array)) {
        array_create(array, default_pool,
                 sizeof(seq) + aligned_record_size,
                 1024 / (sizeof(seq) + aligned_record_size));
    }
    i_assert(array->arr.element_size == sizeof(seq) + aligned_record_size);

    if (mail_index_seq_array_lookup(array, seq, &idx)) {
        /* already there, update */
        p = array_idx_modifiable(array, idx);
        if (old_record != NULL) {
            /* save the old record before overwriting it */
            memcpy(old_record, PTR_OFFSET(p, sizeof(seq)),
                   record_size);
        }
        memcpy(PTR_OFFSET(p, sizeof(seq)), record, record_size);
        return TRUE;
    } else {
        /* insert */
                p = array_insert_space(array, idx);
        memcpy(p, &seq, sizeof(seq));
        memcpy(PTR_OFFSET(p, sizeof(seq)), record, record_size);
        return FALSE;
    }
}

static void
mail_index_buffer_convert_to_uids(struct mail_index_transaction *t,
                  ARRAY_TYPE(seq_array) *array, bool range)
{
        struct mail_index_view *view = t->view;
    const struct mail_index_record *rec;
    uint32_t *seq;
    unsigned int i, j, count, range_count;

    if (!array_is_created(array))
        return;

    count = array_count(array);
    range_count = range ? 1 : 0;
    for (i = 0; i < count; i++) {
        seq = array_idx_modifiable(array, i);

        for (j = 0; j <= range_count; j++, seq++) {
            i_assert(*seq > 0);

            if (*seq >= t->first_new_seq)
                rec = mail_index_transaction_lookup(t, *seq);
            else {
                i_assert(*seq <= view->map->hdr.messages_count);
                rec = MAIL_INDEX_MAP_IDX(view->map, *seq - 1);
            }

            /* we're using only rec->uid, no need to bother locking
               the index. */
            if (rec->uid == 0) {
                /* FIXME: replace with simple assert once we
                   figure out why this happens.. */
                i_panic("seq = %u, rec->uid = %u, "
                    "first_new_seq = %u, messages = %u",
                    *seq, rec->uid, t->first_new_seq,
                    view->map->hdr.messages_count);
            }
            *seq = rec->uid;
        }
    }
}

static void keyword_updates_convert_to_uids(struct mail_index_transaction *t)
{
        struct mail_index_transaction_keyword_update *updates;
    unsigned int i, count;

    if (!array_is_created(&t->keyword_updates))
        return;

    updates = array_get_modifiable(&t->keyword_updates, &count);
    for (i = 0; i < count; i++) {
        if (array_is_created(&updates[i].add_seq)) {
            mail_index_buffer_convert_to_uids(t,
                (void *)&updates[i].add_seq, TRUE);
        }
        if (array_is_created(&updates[i].remove_seq)) {
            mail_index_buffer_convert_to_uids(t,
                (void *)&updates[i].remove_seq, TRUE);
        }
    }
}

static int
mail_index_transaction_convert_to_uids(struct mail_index_transaction *t)
{
    ARRAY_TYPE(seq_array) *updates;
    unsigned int i, count;

    if (array_is_created(&t->ext_rec_updates)) {
        updates = array_get_modifiable(&t->ext_rec_updates, &count);
        for (i = 0; i < count; i++) {
            if (!array_is_created(&updates[i]))
                continue;
            mail_index_buffer_convert_to_uids(t, &updates[i],
                              FALSE);
        }
    }

        keyword_updates_convert_to_uids(t);

    mail_index_buffer_convert_to_uids(t, (void *)&t->expunges, TRUE);
    mail_index_buffer_convert_to_uids(t, (void *)&t->updates, TRUE);
    mail_index_buffer_convert_to_uids(t, (void *)&t->keyword_resets, TRUE);
    return 0;
}

struct uid_map {
    uint32_t idx;
    uint32_t uid;
};

static int uid_map_cmp(const void *p1, const void *p2)
{
    const struct uid_map *m1 = p1, *m2 = p2;

    return m1->uid < m2->uid ? -1 :
        (m1->uid > m2->uid ? 1 : 0);
}

static void
mail_index_update_day_headers(struct mail_index_transaction *t)
{
    struct mail_index_header hdr;
    const struct mail_index_record *rec;
    const int max_days =
        sizeof(hdr.day_first_uid) / sizeof(hdr.day_first_uid[0]);
    struct tm tm;
    time_t stamp;
    int i, days;

    hdr = *mail_index_get_header(t->view);
    rec = array_idx(&t->appends, 0);

    /* get beginning of today */
    tm = *localtime(&ioloop_time);
    tm.tm_hour = 0;
    tm.tm_min = 0;
    tm.tm_sec = 0;
    stamp = mktime(&tm);
    i_assert(stamp != (time_t)-1);

    if ((time_t)hdr.day_stamp >= stamp)
        return;

    /* get number of days since last message */
    days = (stamp - hdr.day_stamp) / (3600*24);
    if (days > max_days)
        days = max_days;

    /* @UNSAFE: move days forward and fill the missing days with old
       day_first_uid[0]. */
    memcpy(hdr.day_first_uid + days, hdr.day_first_uid, max_days - days);
    for (i = 1; i < days; i++)
        hdr.day_first_uid[i] = hdr.day_first_uid[0];

    hdr.day_stamp = stamp;
    hdr.day_first_uid[0] = rec->uid;

    mail_index_update_header(t,
        offsetof(struct mail_index_header, day_stamp),
        &hdr.day_stamp, sizeof(hdr.day_stamp), FALSE);
    mail_index_update_header(t,
        offsetof(struct mail_index_header, day_first_uid),
        hdr.day_first_uid, sizeof(hdr.day_first_uid), FALSE);
}

void mail_index_transaction_sort_appends(struct mail_index_transaction *t)
{
    struct mail_index_record *recs, *sorted_recs;
    struct uid_map *new_uid_map;
    ARRAY_TYPE(seq_array) *ext_rec_arrays;
    uint32_t *old_to_new_map;
    unsigned int i, j, count, ext_rec_array_count;

    if (!t->appends_nonsorted)
        return;

    /* first make a copy of the UIDs and map them to sequences */
    recs = array_get_modifiable(&t->appends, &count);
    new_uid_map = i_new(struct uid_map, count);
    for (i = 0; i < count; i++) {
        new_uid_map[i].idx = i;
        new_uid_map[i].uid = recs[i].uid;
    }

    /* now sort the UID map */
    qsort(new_uid_map, count, sizeof(*new_uid_map), uid_map_cmp);

    old_to_new_map = i_new(uint32_t, count);
    for (i = 0; i < count; i++)
        old_to_new_map[new_uid_map[i].idx] = i;

    /* sort mail records */
    sorted_recs = i_new(struct mail_index_record, count);
    for (i = 0; i < count; i++)
        sorted_recs[i] = recs[new_uid_map[i].idx];
    buffer_write(t->appends.arr.buffer, 0, sorted_recs,
             sizeof(*sorted_recs) * count);
    i_free(sorted_recs);

    /* fix the order in extensions */
    if (!array_is_created(&t->ext_rec_updates)) {
        ext_rec_arrays = NULL;
        ext_rec_array_count = 0;
    } else {
        ext_rec_arrays = array_get_modifiable(&t->ext_rec_updates,
                              &ext_rec_array_count);
    }
    for (j = 0; j < ext_rec_array_count; j++) {
        ARRAY_TYPE(seq_array) *old_array = &ext_rec_arrays[j];
        ARRAY_TYPE(seq_array) new_array;
        unsigned int ext_count;
        const uint32_t *ext_rec;
        uint32_t seq;

        if (!array_is_created(old_array))
            continue;

        ext_count = array_count(old_array);
        array_create(&new_array, default_pool,
                 old_array->arr.element_size, ext_count);
        for (i = 0; i < ext_count; i++) {
            ext_rec = array_idx(old_array, i);

            seq = *ext_rec < t->first_new_seq ? *ext_rec :
                (t->first_new_seq +
                 old_to_new_map[*ext_rec - t->first_new_seq]);
            mail_index_seq_array_add(&new_array, seq, ext_rec+1,
                         old_array->arr.element_size -
                         sizeof(*ext_rec), NULL);
        }
        array_free(old_array);
        ext_rec_arrays[j] = new_array;
    }

    /* FIXME: fix the order in keywords */

    i_free(new_uid_map);
    i_free(old_to_new_map);

    t->appends_nonsorted = FALSE;
}

uint32_t mail_index_transaction_get_next_uid(struct mail_index_transaction *t)
{
    const struct mail_index_header *hdr;
    const struct mail_index_record *recs;
    unsigned int count, offset;
    uint32_t next_uid;

    next_uid = t->reset ? 1 : t->view->map->hdr.next_uid;
    if (array_is_created(&t->appends)) {
        /* get next_uid from appends if they have UIDs */
        mail_index_transaction_sort_appends(t);

        recs = array_get(&t->appends, &count);
        if (count > 0 && recs[count-1].uid != 0) {
            i_assert(recs[count-1].uid >= next_uid);
            next_uid = recs[count-1].uid + 1;
        }
    }

    /* see if it's been updated in pre/post header changes */
    offset = offsetof(struct mail_index_header, next_uid);
    if (t->post_hdr_mask[offset] != 0) {
        hdr = (const void *)t->post_hdr_change;
        if (hdr->next_uid > next_uid)
            next_uid = hdr->next_uid;
    }
    if (t->pre_hdr_mask[offset] != 0) {
        hdr = (const void *)t->pre_hdr_change;
        if (hdr->next_uid > next_uid)
            next_uid = hdr->next_uid;
    }
    return next_uid;
}

static int _mail_index_transaction_commit(struct mail_index_transaction *t,
                      uint32_t *log_file_seq_r,
                      uoff_t *log_file_offset_r)
{
    int ret;

    i_assert(t->first_new_seq >
         mail_index_view_get_messages_count(t->view));

    if (t->cache_trans_ctx != NULL) {
        mail_cache_transaction_commit(t->cache_trans_ctx);
                t->cache_trans_ctx = NULL;
    }

    if (array_is_created(&t->appends)) {
        mail_index_transaction_sort_appends(t);
        mail_index_update_day_headers(t);
    }

    if (mail_index_transaction_convert_to_uids(t) < 0)
        ret = -1;
    else {
        ret = mail_transaction_log_append(t, log_file_seq_r,
                          log_file_offset_r);
    }

    mail_index_transaction_unref(&t);
    return ret;
}

static void _mail_index_transaction_rollback(struct mail_index_transaction *t)
{
    if (t->cache_trans_ctx != NULL) {
        mail_cache_transaction_rollback(t->cache_trans_ctx);
                t->cache_trans_ctx = NULL;
    }
        mail_index_transaction_unref(&t);
}

int mail_index_transaction_commit(struct mail_index_transaction **_t,
                  uint32_t *log_file_seq_r,
                  uoff_t *log_file_offset_r)
{
    struct mail_index_transaction *t = *_t;

    if (mail_index_view_is_inconsistent(t->view)) {
        mail_index_transaction_rollback(_t);
        return -1;
    }

    *_t = NULL;
    return t->v.commit(t, log_file_seq_r, log_file_offset_r);
}

void mail_index_transaction_rollback(struct mail_index_transaction **_t)
{
    struct mail_index_transaction *t = *_t;

    *_t = NULL;
    t->v.rollback(t);
}

struct mail_index_record *
mail_index_transaction_lookup(struct mail_index_transaction *t, uint32_t seq)
{
    i_assert(seq >= t->first_new_seq && seq <= t->last_new_seq);

    return array_idx_modifiable(&t->appends, seq - t->first_new_seq);
}

void mail_index_append(struct mail_index_transaction *t, uint32_t uid,
               uint32_t *seq_r)
{
        struct mail_index_record *rec;

    i_assert(!t->no_appends);

    t->log_updates = TRUE;

    if (!array_is_created(&t->appends))
        i_array_init(&t->appends, 32);

    /* sequence number is visible only inside given view,
       so let it generate it */
    if (t->last_new_seq != 0)
        *seq_r = ++t->last_new_seq;
    else
        *seq_r = t->last_new_seq = t->first_new_seq;

    rec = array_append_space(&t->appends);
    if (uid != 0) {
        rec->uid = uid;
        if (!t->appends_nonsorted &&
            t->last_new_seq != t->first_new_seq) {
            /* if previous record's UID is larger than this one,
               we'll have to sort the appends later */
            rec = mail_index_transaction_lookup(t, *seq_r - 1);
            if (rec->uid > uid)
                t->appends_nonsorted = TRUE;
        }
    }
}

void mail_index_append_assign_uids(struct mail_index_transaction *t,
                   uint32_t first_uid, uint32_t *next_uid_r)
{
    struct mail_index_record *recs;
    unsigned int i, count;

    i_assert(first_uid != 0);

    if (!array_is_created(&t->appends))
        return;

    recs = array_get_modifiable(&t->appends, &count);

    /* find the first mail with uid = 0 */
    for (i = 0; i < count; i++) {
        if (recs[i].uid == 0)
            break;
    }

    for (; i < count; i++) {
        i_assert(recs[i].uid == 0);
        recs[i].uid = first_uid++;
    }

    *next_uid_r = first_uid;
}

void mail_index_expunge(struct mail_index_transaction *t, uint32_t seq)
{
    i_assert(seq > 0 && seq <= mail_index_view_get_messages_count(t->view));

    t->log_updates = TRUE;

    /* expunges is a sorted array of {seq1, seq2, ..}, .. */
    seq_range_array_add(&t->expunges, 128, seq);
}

static bool
mail_transaction_update_want_add(struct mail_index_transaction *t,
                 const struct mail_transaction_flag_update *u)
{
    const struct mail_index_record *rec;
    uint32_t seq;

    if ((t->flags & MAIL_INDEX_TRANSACTION_FLAG_AVOID_FLAG_UPDATES) == 0)
        return TRUE;

    for (seq = u->uid1; seq <= u->uid2; seq++) {
        if (mail_index_lookup(t->view, seq, &rec) < 0)
            return TRUE;

        if ((rec->flags & u->add_flags) != u->add_flags ||
            (rec->flags & u->remove_flags) != 0)
            return TRUE;
    }

    return FALSE;
}

static void
mail_index_insert_flag_update(struct mail_index_transaction *t,
                  struct mail_transaction_flag_update u,
                  uint32_t left_idx, uint32_t right_idx)
{
    struct mail_transaction_flag_update *updates, tmp_update;
    unsigned int count;
    uint32_t idx, move;

    updates = array_get_modifiable(&t->updates, &count);

    i_assert(left_idx <= right_idx && right_idx <= count);

    /* find the first update with either overlapping range,
       or the update which will come after our insert */
    idx = left_idx;
    while (left_idx < right_idx) {
        idx = (left_idx + right_idx) / 2;

        if (updates[idx].uid2 < u.uid1)
            left_idx = idx+1;
        else if (updates[idx].uid1 > u.uid1)
            right_idx = idx;
        else
            break;
    }
    if (idx < count && updates[idx].uid2 < u.uid1)
        idx++;

    /* overlapping ranges, split/merge them */
    i_assert(idx == 0 || updates[idx-1].uid2 < u.uid1);
    i_assert(idx == count || updates[idx].uid2 >= u.uid1);

    for (; idx < count && u.uid2 >= updates[idx].uid1; idx++) {
        if (u.uid1 != updates[idx].uid1 &&
            (updates[idx].add_flags != u.add_flags ||
             updates[idx].remove_flags != u.remove_flags)) {
            if (u.uid1 < updates[idx].uid1) {
                /* insert new update */
                tmp_update = u;
                tmp_update.uid2 = updates[idx].uid1 - 1;
                move = 0;
            } else {
                /* split existing update from beginning */
                tmp_update = updates[idx];
                tmp_update.uid2 = u.uid1 - 1;
                updates[idx].uid1 = u.uid1;
                move = 1;
            }

            i_assert(tmp_update.uid1 <= tmp_update.uid2);
            i_assert(updates[idx].uid1 <= updates[idx].uid2);

            if (mail_transaction_update_want_add(t, &tmp_update)) {
                array_insert(&t->updates, idx, &tmp_update, 1);
                updates = array_get_modifiable(&t->updates,
                                   &count);
                idx += move;
            }
        } else if (u.uid1 < updates[idx].uid1) {
            updates[idx].uid1 = u.uid1;
        }

        if (u.uid2 < updates[idx].uid2 &&
            (updates[idx].add_flags != u.add_flags ||
             updates[idx].remove_flags != u.remove_flags)) {
            /* split existing update from end */
            tmp_update = updates[idx];
            tmp_update.uid2 = u.uid2;
            updates[idx].uid1 = u.uid2 + 1;

            i_assert(tmp_update.uid1 <= tmp_update.uid2);
            i_assert(updates[idx].uid1 <= updates[idx].uid2);

            if (mail_transaction_update_want_add(t, &tmp_update))
                array_insert(&t->updates, idx, &tmp_update, 1);
            updates = array_get_modifiable(&t->updates, &count);
        }

        updates[idx].add_flags =
            (updates[idx].add_flags | u.add_flags) &
            ~u.remove_flags;
        updates[idx].remove_flags =
            (updates[idx].remove_flags | u.remove_flags) &
            ~u.add_flags;
        u.uid1 = updates[idx].uid2 + 1;

        if (updates[idx].add_flags == 0 &&
            updates[idx].remove_flags == 0) {
            /* we can remove this update completely */
            array_delete(&t->updates, idx, 1);
            updates = array_get_modifiable(&t->updates, &count);
            idx--;
        }

        if (u.uid1 > u.uid2) {
            /* break here before idx++ so last_update_idx is set
               correctly */
            break;
        }
    }
    i_assert(idx <= count);

    if (u.uid1 <= u.uid2) {
        i_assert(idx == 0 || updates[idx-1].uid2 < u.uid1);
        i_assert(idx == count || updates[idx].uid1 > u.uid2);
        if (mail_transaction_update_want_add(t, &u)) {
            array_insert(&t->updates, idx, &u, 1);
            count++;
        }
    }
    t->last_update_idx = idx == count ? count-1 : idx;
}

static void mail_index_record_modify_flags(struct mail_index_record *rec,
                       enum modify_type modify_type,
                       enum mail_flags flags)
{
    switch (modify_type) {
    case MODIFY_REPLACE:
        rec->flags = flags;
        break;
    case MODIFY_ADD:
        rec->flags |= flags;
        break;
    case MODIFY_REMOVE:
        rec->flags &= ~flags;
        break;
    }
}

void mail_index_update_flags_range(struct mail_index_transaction *t,
                   uint32_t seq1, uint32_t seq2,
                   enum modify_type modify_type,
                   enum mail_flags flags)
{
    struct mail_index_record *rec;
    struct mail_transaction_flag_update u, *last_update;
    unsigned int first_idx, count;

    if (seq2 >= t->first_new_seq) {
        /* updates for appended messages, modify them directly */
        uint32_t seq;

        for (seq = I_MAX(t->first_new_seq, seq1); seq <= seq2; seq++) {
            rec = mail_index_transaction_lookup(t, seq);
            mail_index_record_modify_flags(rec, modify_type, flags);
        }
        if (seq1 >= t->first_new_seq)
            return;

        /* range contains also existing messages. update them next. */
        seq2 = t->first_new_seq - 1;
    }

    i_assert(seq1 <= seq2 && seq1 > 0);
    i_assert(seq2 <= mail_index_view_get_messages_count(t->view));

    memset(&u, 0, sizeof(u));
    u.uid1 = seq1;
    u.uid2 = seq2;

    switch (modify_type) {
    case MODIFY_REPLACE:
        u.add_flags = flags;
        u.remove_flags = ~flags & MAIL_INDEX_FLAGS_MASK;
        break;
    case MODIFY_ADD:
        u.add_flags = flags;
        break;
    case MODIFY_REMOVE:
        u.remove_flags = flags;
        break;
    }

    if (!array_is_created(&t->updates)) {
        i_array_init(&t->updates, 256);
        if (mail_transaction_update_want_add(t, &u))
            array_append(&t->updates, &u, 1);
        return;
    }

    last_update = array_get_modifiable(&t->updates, &count);
    if (t->last_update_idx < count) {
        /* fast path - hopefully we're updating the next message,
           or a message that is to be appended as last update */
        last_update += t->last_update_idx;
        if (seq1 - 1 == last_update->uid2) {
            if (u.add_flags == last_update->add_flags &&
                u.remove_flags == last_update->remove_flags &&
                (t->last_update_idx + 1 == count ||
                 last_update[1].uid1 > seq2)) {
                /* we can just update the UID range */
                last_update->uid2 = seq2;
                return;
            }
        } else if (seq1 > last_update->uid2) {
            /* hopefully we can just append it */
            t->last_update_idx++;
            last_update++;
        }
    }

    if (t->last_update_idx == count) {
        if (mail_transaction_update_want_add(t, &u))
            array_append(&t->updates, &u, 1);
        else if (t->last_update_idx > 0)
            t->last_update_idx--;
    } else {
        i_assert(t->last_update_idx < count);

        /* slow path */
        if (seq1 > last_update->uid2) {
            /* added after this */
            first_idx = t->last_update_idx + 1;
        } else {
            /* added before this or on top of this */
            first_idx = 0;
            count = t->last_update_idx + 1;
        }
        mail_index_insert_flag_update(t, u, first_idx, count);
    }
}

void mail_index_update_flags(struct mail_index_transaction *t, uint32_t seq,
                 enum modify_type modify_type,
                 enum mail_flags flags)
{
    mail_index_update_flags_range(t, seq, seq, modify_type, flags);
}

void mail_index_update_header(struct mail_index_transaction *t,
                  size_t offset, const void *data, size_t size,
                  bool prepend)
{
    i_assert(offset < sizeof(t->pre_hdr_change));
    i_assert(size <= sizeof(t->pre_hdr_change) - offset);

    t->log_updates = TRUE;

    if (prepend) {
        t->pre_hdr_changed = TRUE;
        memcpy(t->pre_hdr_change + offset, data, size);
        for (; size > 0; size--)
            t->pre_hdr_mask[offset++] = 1;
    } else {
        t->post_hdr_changed = TRUE;
        memcpy(t->post_hdr_change + offset, data, size);
        for (; size > 0; size--)
            t->post_hdr_mask[offset++] = 1;
    }
}

void mail_index_ext_resize(struct mail_index_transaction *t, uint32_t ext_id,
               uint32_t hdr_size, uint16_t record_size,
               uint16_t record_align)
{
    struct mail_transaction_ext_intro intro;
    uint32_t old_record_size, old_record_align;

    memset(&intro, 0, sizeof(intro));

    /* get ext_id from transaction's map if it's there */
    if (!mail_index_map_get_ext_idx(t->view->map, ext_id, &intro.ext_id)) {
        /* have to create it */
        const struct mail_index_registered_ext *rext;

        intro.ext_id = (uint32_t)-1;
        rext = array_idx(&t->view->index->extensions, ext_id);
        old_record_size = rext->record_size;
        old_record_align = rext->record_align;
    } else {
        const struct mail_index_ext *ext;

        ext = array_idx(&t->view->map->extensions, ext_id);
        old_record_size = ext->record_size;
        old_record_align = ext->record_align;
    }

    /* allow only header size changes if extension records have already
       been changed in transaction */
    i_assert(!array_is_created(&t->ext_rec_updates) ||
         (old_record_size == record_size &&
          old_record_align == record_align));

    t->log_ext_updates = TRUE;

    if (!array_is_created(&t->ext_resizes))
        i_array_init(&t->ext_resizes, ext_id + 2);

    intro.hdr_size = hdr_size;
    intro.record_size = record_size;
    intro.record_align = record_align;
    intro.name_size = 1;
    array_idx_set(&t->ext_resizes, ext_id, &intro);
}

void mail_index_ext_reset(struct mail_index_transaction *t, uint32_t ext_id,
              uint32_t reset_id)
{
    i_assert(reset_id != 0);

    mail_index_ext_set_reset_id(t, ext_id, reset_id);

    if (!array_is_created(&t->ext_resets))
        i_array_init(&t->ext_resets, ext_id + 2);
    array_idx_set(&t->ext_resets, ext_id, &reset_id);
    t->log_ext_updates = TRUE;
}

static bool
mail_index_transaction_has_ext_changes(struct mail_index_transaction *t)
{
    unsigned int i, count;

    if (array_is_created(&t->ext_rec_updates)) {
        const ARRAY_TYPE(seq_array) *array;

        array = array_get(&t->ext_rec_updates, &count);
        for (i = 0; i < count; i++) {
            if (array_is_created(&array[i]))
                return TRUE;
        }
    }
    if (array_is_created(&t->ext_hdr_updates)) {
        struct mail_index_transaction_ext_hdr_update *const *hdr;

        hdr = array_get(&t->ext_hdr_updates, &count);
        for (i = 0; i < count; i++) {
            if (hdr[i] != NULL)
                return TRUE;
        }
    }
    if (array_is_created(&t->ext_resets)) {
        const uint32_t *ids;

        ids = array_get(&t->ext_resets, &count);
        for (i = 0; i < count; i++) {
            if (ids[i] != 0)
                return TRUE;
        }
    }
    if (array_is_created(&t->ext_resizes)) {
        const struct mail_transaction_ext_intro *resizes;

        resizes = array_get(&t->ext_resizes, &count);
        for (i = 0; i < count; i++) {
            if (resizes[i].name_size > 0)
                return TRUE;
        }
    }
    return FALSE;
}

void mail_index_ext_set_reset_id(struct mail_index_transaction *t,
                 uint32_t ext_id, uint32_t reset_id)
{
    if (array_is_created(&t->ext_rec_updates) &&
        ext_id < array_count(&t->ext_rec_updates)) {
        /* if extension records have been updated, clear them */
        ARRAY_TYPE(seq_array) *array;

        array = array_idx_modifiable(&t->ext_rec_updates, ext_id);
        if (array_is_created(array))
            array_clear(array);
    }
    if (array_is_created(&t->ext_hdr_updates) &&
        ext_id < array_count(&t->ext_hdr_updates)) {
        /* if extension headers have been updated, clear them */
        struct mail_index_transaction_ext_hdr_update **hdr;

        hdr = array_idx_modifiable(&t->ext_hdr_updates, ext_id);
        if (*hdr != NULL)
            i_free_and_null(*hdr);
    }
    if (array_is_created(&t->ext_resets) &&
        ext_id < array_count(&t->ext_resets)) {
        /* clear resets */
        array_idx_clear(&t->ext_resets, ext_id);
    }
    if (array_is_created(&t->ext_resizes) &&
        ext_id < array_count(&t->ext_resizes)) {
        /* clear resizes */
        array_idx_clear(&t->ext_resizes, ext_id);
    }

    if (!array_is_created(&t->ext_reset_ids))
        i_array_init(&t->ext_reset_ids, ext_id + 2);
    array_idx_set(&t->ext_reset_ids, ext_id, &reset_id);

    t->log_ext_updates = mail_index_transaction_has_ext_changes(t);
}

void mail_index_update_header_ext(struct mail_index_transaction *t,
                  uint32_t ext_id, size_t offset,
                  const void *data, size_t size)
{
    struct mail_index_transaction_ext_hdr_update *hdr, **pos;

    hdr = i_malloc(sizeof(*hdr) + size);
    hdr->ext_id = ext_id;
    hdr->offset = offset;
    hdr->size = size;
    memcpy(hdr + 1, data, size);

    if (!array_is_created(&t->ext_hdr_updates))
        i_array_init(&t->ext_hdr_updates, ext_id + 2);

    pos = array_idx_modifiable(&t->ext_hdr_updates, ext_id);
    if (*pos != NULL) {
        i_panic("mail_index_update_header_ext() doesn't currently "
            "support multiple updates to the same ext header");
    }
    *pos = hdr;

    t->log_ext_updates = TRUE;
}

void mail_index_update_ext(struct mail_index_transaction *t, uint32_t seq,
               uint32_t ext_id, const void *data, void *old_data_r)
{
    struct mail_index *index = t->view->index;
        const struct mail_index_registered_ext *rext;
    const struct mail_transaction_ext_intro *intro;
    uint16_t record_size;
    ARRAY_TYPE(seq_array) *array;
    unsigned int count;

    i_assert(seq > 0 &&
         (seq <= mail_index_view_get_messages_count(t->view) ||
          seq <= t->last_new_seq));
    i_assert(ext_id < array_count(&index->extensions));

    t->log_ext_updates = TRUE;

    if (!array_is_created(&t->ext_resizes)) {
        intro = NULL;
        count = 0;
    } else {
        intro = array_get(&t->ext_resizes, &count);
    }
    if (ext_id < count && intro[ext_id].name_size != 0) {
        /* resized record */
        record_size = intro[ext_id].record_size;
    } else {
        rext = array_idx(&index->extensions, ext_id);
        record_size = rext->record_size;
    }

    if (!array_is_created(&t->ext_rec_updates))
        i_array_init(&t->ext_rec_updates, ext_id + 2);
    array = array_idx_modifiable(&t->ext_rec_updates, ext_id);

    /* @UNSAFE */
    if (!mail_index_seq_array_add(array, seq, data, record_size,
                      old_data_r)) {
        /* not found, clear old_data if it was given */
        if (old_data_r != NULL)
            memset(old_data_r, 0, record_size);
    }
}

struct mail_keywords *
mail_index_keywords_create(struct mail_index_transaction *t,
               const char *const keywords[])
{
    struct mail_index *index = t->view->index;
    struct mail_keywords *k;
    unsigned int i, count;

    count = strarray_length(keywords);
    if (count == 0) {
        k = i_new(struct mail_keywords, 1);
        k->index = index;
        return k;
    }

    /* @UNSAFE */
    k = i_malloc(sizeof(struct mail_keywords) +
             (sizeof(k->idx) * (count-1)));
    k->index = index;
    k->count = count;

    /* look up the keywords from index. they're never removed from there
       so we can permanently store indexes to them. */
    for (i = 0; i < count; i++) {
        (void)mail_index_keyword_lookup(index, keywords[i],
                        TRUE, &k->idx[i]);
    }
    return k;
}

struct mail_keywords *
mail_index_keywords_create_from_indexes(struct mail_index_transaction *t,
                    const ARRAY_TYPE(keyword_indexes)
                        *keyword_indexes)
{
    struct mail_keywords *k;
    unsigned int count;

    count = array_count(keyword_indexes);
    if (count == 0) {
        k = i_new(struct mail_keywords, 1);
        k->index = t->view->index;
        return k;
    }

    /* @UNSAFE */
    k = i_malloc(sizeof(struct mail_keywords) +
             (sizeof(k->idx) * (count-1)));
    k->index = t->view->index;
    k->count = count;

    memcpy(k->idx, array_idx(keyword_indexes, 0),
           count * sizeof(k->idx[0]));
    return k;
}

void mail_index_keywords_free(struct mail_keywords **keywords)
{
    i_free(*keywords);
    *keywords = NULL;
}

void mail_index_update_keywords(struct mail_index_transaction *t, uint32_t seq,
                enum modify_type modify_type,
                struct mail_keywords *keywords)
{
    struct mail_index_transaction_keyword_update *u;
    unsigned int i, ku_count;

    i_assert(seq > 0 &&
         (seq <= mail_index_view_get_messages_count(t->view) ||
          seq <= t->last_new_seq));
    i_assert(keywords->count > 0 || modify_type == MODIFY_REPLACE);
    i_assert(keywords->index == t->view->index);

    if (!array_is_created(&t->keyword_updates) && keywords->count > 0) {
        uint32_t max_idx = keywords->idx[keywords->count-1];

        i_array_init(&t->keyword_updates, max_idx + 1);
    }

    /* Update add_seq and remove_seq arrays which describe the keyword
       changes. Don't bother updating remove_seq or keyword resets for
       newly added messages since they default to not having any
       keywords anyway. */
    switch (modify_type) {
    case MODIFY_ADD:
        for (i = 0; i < keywords->count; i++) {
            u = array_idx_modifiable(&t->keyword_updates,
                         keywords->idx[i]);
            seq_range_array_add(&u->add_seq, 16, seq);
            if (seq < t->first_new_seq)
                seq_range_array_remove(&u->remove_seq, seq);
        }
        break;
    case MODIFY_REMOVE:
        for (i = 0; i < keywords->count; i++) {
            u = array_idx_modifiable(&t->keyword_updates,
                         keywords->idx[i]);
            seq_range_array_remove(&u->add_seq, seq);
            if (seq < t->first_new_seq)
                seq_range_array_add(&u->remove_seq, 16, seq);
        }
        break;
    case MODIFY_REPLACE:
        /* Remove sequence from all add/remove arrays */
        if (array_is_created(&t->keyword_updates)) {
            u = array_get_modifiable(&t->keyword_updates,
                         &ku_count);
            for (i = 0; i < ku_count; i++) {
                seq_range_array_remove(&u[i].add_seq, seq);
                if (seq < t->first_new_seq) {
                    seq_range_array_remove(
                        &u[i].remove_seq, seq);
                }
            }
        }
        /* Add the wanted keyword back */
        for (i = 0; i < keywords->count; i++) {
            u = array_idx_modifiable(&t->keyword_updates,
                         keywords->idx[i]);
            seq_range_array_add(&u->add_seq, 16, seq);
        }

        if (seq < t->first_new_seq)
            seq_range_array_add(&t->keyword_resets, 16, seq);
        break;
    }

    t->log_updates = TRUE;
}

void mail_index_reset(struct mail_index_transaction *t)
{
    mail_index_transaction_reset(t);

    t->reset = TRUE;
}

struct mail_index_transaction_vfuncs trans_vfuncs = {
    _mail_index_transaction_commit,
    _mail_index_transaction_rollback
};

struct mail_index_transaction *
mail_index_transaction_begin(struct mail_index_view *view,
                 enum mail_index_transaction_flags flags)
{
    struct mail_index_transaction *t;

    /* don't allow syncing view while there's ongoing transactions */
    mail_index_view_transaction_ref(view);
    mail_index_view_ref(view);

    t = i_new(struct mail_index_transaction, 1);
    t->refcount = 1;
    t->v = trans_vfuncs;
    t->view = view;
    t->flags = flags;
    t->sync_transaction = view->index_sync_view;

    if (view->syncing) {
        /* transaction view cannot work if new records are being added
           in two places. make sure it doesn't happen. */
        t->no_appends = TRUE;
        t->first_new_seq = (uint32_t)-1;
    } else {
        t->first_new_seq =
            mail_index_view_get_messages_count(t->view) + 1;
    }

    i_array_init(&t->module_contexts,
             I_MIN(5, mail_index_module_register.id));

    if (hook_mail_index_transaction_created != NULL)
        hook_mail_index_transaction_created(t);
    return t;
}