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

	mail-index-transaction.c revision a2cbf1d392ee983520451bc9b849a490f28ac298
2454dfa32c93c20a8522c6ed42fe057baaac9f9aStephan Bosch/* Copyright (C) 2003-2004 Timo Sirainen */
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen/* Inside transaction we keep messages stored in sequences in uid fields.
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen   Before they're written to transaction log the sequences are changed to
5e327e031d1591f8bff17b67eba7139afbd36cddTimo Sirainen   UIDs. This is because we're able to compress sequence ranges better. */
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen#include "lib.h"
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen#include "ioloop.h"
a2fdfd2efdbb2d912aad23900a466cf74114920bTimo Sirainen#include "array.h"
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen#include "seq-range-array.h"
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi#include "mail-index-view-private.h"
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen#include "mail-transaction-log.h"
c6be98b5270900746f35ebe28bd636019976e29eTimo Sirainen#include "mail-cache-private.h"
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen#include "mail-index-transaction-private.h"
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen#include <stddef.h>
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi#include <stdlib.h>
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen#include <time.h>
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainenvoid (*hook_mail_index_transaction_created)
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi        (struct mail_index_transaction *t) = NULL;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainenvoid mail_index_transaction_reset(struct mail_index_transaction *t)
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen{
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    ARRAY_TYPE(seq_array) *recs;
5e327e031d1591f8bff17b67eba7139afbd36cddTimo Sirainen    struct mail_index_transaction_ext_hdr_update **ext_hdrs;
5fbccc935e3f7b916aa7c6e302a212821072e83aTimo Sirainen    unsigned i, count;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
f36c4185474823594a78b3f252e79d8923522c36Timo Sirainen    if (array_is_created(&t->ext_rec_updates)) {
f36c4185474823594a78b3f252e79d8923522c36Timo Sirainen        recs = array_get_modifiable(&t->ext_rec_updates, &count);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        for (i = 0; i < count; i++) {
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen            if (array_is_created(&recs[i]))
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen                array_free(&recs[i]);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        }
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        array_free(&t->ext_rec_updates);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    }
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    if (array_is_created(&t->ext_hdr_updates)) {
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        ext_hdrs = array_get_modifiable(&t->ext_hdr_updates, &count);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        for (i = 0; i < count; i++)
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen            i_free(ext_hdrs[i]);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        array_free(&t->ext_hdr_updates);
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi    }
f300f927771a39549ce6cb7607129508e9041b4aStephan Bosch
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi    if (array_is_created(&t->keyword_updates)) {
e60c3e17c656c53da60f0ac51aa15e9ef2742d77Stephan Bosch        struct mail_index_transaction_keyword_update *u;
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi        u = array_get_modifiable(&t->keyword_updates, &count);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        for (i = 0; i < count; i++) {
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen            if (array_is_created(&u[i].add_seq))
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen                array_free(&u[i].add_seq);
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen            if (array_is_created(&u[i].remove_seq))
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen                array_free(&u[i].remove_seq);
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen        }
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen        array_free(&t->keyword_updates);
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi    }
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi    if (array_is_created(&t->keyword_resets))
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi        array_free(&t->keyword_resets);
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi    if (array_is_created(&t->appends))
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi        array_free(&t->appends);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    if (array_is_created(&t->expunges))
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        array_free(&t->expunges);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    if (array_is_created(&t->updates))
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        array_free(&t->updates);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    if (array_is_created(&t->ext_resizes))
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        array_free(&t->ext_resizes);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    if (array_is_created(&t->ext_resets))
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        array_free(&t->ext_resets);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
f36c4185474823594a78b3f252e79d8923522c36Timo Sirainen    t->first_new_seq = mail_index_view_get_messages_count(t->view)+1;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    t->last_new_seq = 0;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    t->last_update_idx = 0;
f36c4185474823594a78b3f252e79d8923522c36Timo Sirainen
5e327e031d1591f8bff17b67eba7139afbd36cddTimo Sirainen    memset(t->pre_hdr_mask, 0, sizeof(t->pre_hdr_mask));
5e327e031d1591f8bff17b67eba7139afbd36cddTimo Sirainen    memset(t->post_hdr_mask, 0, sizeof(t->post_hdr_mask));
5e327e031d1591f8bff17b67eba7139afbd36cddTimo Sirainen
5e327e031d1591f8bff17b67eba7139afbd36cddTimo Sirainen    if (t->cache_trans_ctx != NULL) {
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        mail_cache_transaction_rollback(t->cache_trans_ctx);
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi                t->cache_trans_ctx = NULL;
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen    }
a13b1245bee0b6524b4aeb3c8fd9e34af648b746Aki Tuomi
c6be98b5270900746f35ebe28bd636019976e29eTimo Sirainen    t->appends_nonsorted = FALSE;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    t->pre_hdr_changed = FALSE;
a2fdfd2efdbb2d912aad23900a466cf74114920bTimo Sirainen    t->post_hdr_changed = FALSE;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    t->reset = FALSE;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    t->log_updates = FALSE;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    t->log_ext_updates = FALSE;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen}
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainenstatic void mail_index_transaction_free(struct mail_index_transaction *t)
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen{
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    mail_index_transaction_reset(t);
c6be98b5270900746f35ebe28bd636019976e29eTimo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    array_free(&t->module_contexts);
a2fdfd2efdbb2d912aad23900a466cf74114920bTimo Sirainen    mail_index_view_transaction_unref(t->view);
237a6211c7fc4d6dbb58dd0467da6dba1b8f21f6Timo Sirainen    mail_index_view_close(&t->view);
45ead232666a47819e89dc71dec57767340d0b62Timo Sirainen    i_free(t);
1e11a94ec50fc9b57eb2c859771c6a326ccaf86fAki Tuomi}
f36c4185474823594a78b3f252e79d8923522c36Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainenstruct mail_index_view *
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainenmail_index_transaction_get_view(struct mail_index_transaction *t)
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen{
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    return t->view;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen}
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainenbool mail_index_transaction_is_expunged(struct mail_index_transaction *t,
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen                    uint32_t seq)
2d1892aaeb63b9774237b6e60d6bb04bf6f8259cTimo Sirainen{
2d1892aaeb63b9774237b6e60d6bb04bf6f8259cTimo Sirainen    return array_is_created(&t->expunges) &&
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen        seq_range_exists(&t->expunges, seq);
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen}
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainenvoid mail_index_transaction_ref(struct mail_index_transaction *t)
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen{
2d1892aaeb63b9774237b6e60d6bb04bf6f8259cTimo Sirainen    t->refcount++;
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen}
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainenvoid mail_index_transaction_unref(struct mail_index_transaction **_t)
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen{
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen    struct mail_index_transaction *t = *_t;
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen    *_t = NULL;
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen    if (--t->refcount == 0)
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen        mail_index_transaction_free(t);
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen}
107659c01b2359b0ee426bde020c8d4e29ede30dTimo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainenbool mail_index_seq_array_lookup(const ARRAY_TYPE(seq_array) *array,
efe78d3ba24fc866af1c79b9223dc0809ba26cadStephan Bosch                 uint32_t seq, unsigned int *idx_r)
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen{
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen    unsigned int idx, left_idx, right_idx, count;
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen    const uint32_t *seq_p;
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen    count = array_count(array);
c1fc5a97a15332f1253ee13a9cab65a7b4b6cd5fTimo Sirainen    if (count == 0) {
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        *idx_r = 0;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        return FALSE;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    }
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    /* we're probably appending it, check */
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    seq_p = array_idx(array, count-1);
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    if (*seq_p < seq)
d6b3cfd855c0eebed68be50d3111de1b5a6afeb0Timo Sirainen        idx = count;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen    else {
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        idx = 0; left_idx = 0; right_idx = count;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen        while (left_idx < right_idx) {
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen            idx = (left_idx + right_idx) / 2;
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen
71df09024cea5f2faa93da3bb9513ee96ba6bf22Timo Sirainen            seq_p = array_idx(array, idx);
            if (*seq_p < seq)
                left_idx = idx+1;
            else if (*seq_p > seq)
                right_idx = idx;
            else {
                *idx_r = idx;
                return TRUE;
            }
        }
    }

    *idx_r = idx;
    return FALSE;
}

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->records_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, records = %u",
                    *seq, rec->uid, t->first_new_seq,
                    view->map->records_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;
}

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(!t->hide_transaction);
    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 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);

            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);

            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 (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);
        array_insert(&t->updates, idx, &u, 1);
    }
    t->last_update_idx = 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 count;

    t->log_updates = TRUE;

    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);
        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) {
        array_append(&t->updates, &u, 1);
        return;
    }

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

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;
    t->log_updates = 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,
                 bool hide, bool external)
{
    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->hide_transaction = hide;
    t->external = external;
    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;
}