ex_stat.c

Shows how to access database and table statistics.

/*-
 * Public Domain 2014-2015 MongoDB, Inc.
 * Public Domain 2008-2014 WiredTiger, Inc.
 *
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * ex_stat.c
 *      This is an example demonstrating how to query database statistics.
 */

#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <wiredtiger.h>

int print_cursor(WT_CURSOR *);
int print_database_stats(WT_SESSION *);
int print_file_stats(WT_SESSION *);
int print_overflow_pages(WT_SESSION *);
int get_stat(WT_CURSOR *cursor, int stat_field, uint64_t *valuep);
int print_derived_stats(WT_SESSION *);

static const char *home;

int
print_cursor(WT_CURSOR *cursor)
{
        const char *desc, *pvalue;
        uint64_t value;
        int ret;

        while ((ret = cursor->next(cursor)) == 0 &&
            (ret = cursor->get_value(cursor, &desc, &pvalue, &value)) == 0)
                if (value != 0)
                        printf("%s=%s\n", desc, pvalue);

        return (ret == WT_NOTFOUND ? 0 : ret);
}
int 
print_database_stats(WT_SESSION *session)
{
        WT_CURSOR *cursor;
        int ret;

        if ((ret = session->open_cursor(session,
            "statistics:", NULL, NULL, &cursor)) != 0)
                return (ret);

        ret = print_cursor(cursor);
        ret = cursor->close(cursor);
        return (ret);
}

int 
print_file_stats(WT_SESSION *session)
{
        WT_CURSOR *cursor;
        int ret;

        if ((ret = session->open_cursor(session,
            "statistics:table:access", NULL, NULL, &cursor)) != 0)
                return (ret);

        ret = print_cursor(cursor);
        ret = cursor->close(cursor);
        return (ret);
}

int 
print_overflow_pages(WT_SESSION *session)
{
        WT_CURSOR *cursor;
        const char *desc, *pvalue;
        uint64_t value;
        int ret;

        if ((ret = session->open_cursor(session,
            "statistics:table:access", NULL, NULL, &cursor)) != 0)
                return (ret);

        cursor->set_key(cursor, WT_STAT_DSRC_BTREE_OVERFLOW);
        ret = cursor->search(cursor);
        ret = cursor->get_value(cursor, &desc, &pvalue, &value);
        printf("%s=%s\n", desc, pvalue);

        ret = cursor->close(cursor);
        return (ret);
}

int
get_stat(WT_CURSOR *cursor, int stat_field, uint64_t *valuep)
{
        const char *desc, *pvalue;
        int ret;

        cursor->set_key(cursor, stat_field);
        if ((ret = cursor->search(cursor)) != 0)
                return (ret);

        return (cursor->get_value(cursor, &desc, &pvalue, valuep));
}
int
print_derived_stats(WT_SESSION *session)
{
        WT_CURSOR *cursor;
        int ret;

        if ((ret = session->open_cursor(session,
            "statistics:table:access", NULL, NULL, &cursor)) != 0)
                return (ret);
        {
        uint64_t ckpt_size, file_size, percent;
        ret = get_stat(cursor, WT_STAT_DSRC_BLOCK_CHECKPOINT_SIZE, &ckpt_size);
        ret = get_stat(cursor, WT_STAT_DSRC_BLOCK_SIZE, &file_size);

        percent = 0;
        if (file_size != 0)
                percent = 100 * ((file_size - ckpt_size) / file_size);
        printf("Table is %" PRIu64 "%% fragmented\n", percent);
        }

        {
        uint64_t app_insert, app_remove, app_update, fs_writes;

        ret = get_stat(cursor, WT_STAT_DSRC_CURSOR_INSERT_BYTES, &app_insert);
        ret = get_stat(cursor, WT_STAT_DSRC_CURSOR_REMOVE_BYTES, &app_remove);
        ret = get_stat(cursor, WT_STAT_DSRC_CURSOR_UPDATE_BYTES, &app_update);

        ret = get_stat(cursor, WT_STAT_DSRC_CACHE_BYTES_WRITE, &fs_writes);

        if (app_insert + app_remove + app_update != 0)
                printf("Write amplification is %.2lf\n",
                    (double)fs_writes / (app_insert + app_remove + app_update));
        }

        ret = cursor->close(cursor);

        return (ret);
}

int
main(void)
{
        WT_CONNECTION *conn;
        WT_CURSOR *cursor;
        WT_SESSION *session;
        int ret;

        /*
         * Create a clean test directory for this run of the test program if the
         * environment variable isn't already set (as is done by make check).
         */
        if (getenv("WIREDTIGER_HOME") == NULL) {
                home = "WT_HOME";
                ret = system("rm -rf WT_HOME && mkdir WT_HOME");
        } else
                home = NULL;

        ret = wiredtiger_open(home, NULL, "create,statistics=(all)", &conn);
        ret = conn->open_session(conn, NULL, NULL, &session);
        ret = session->create(
            session, "table:access", "key_format=S,value_format=S");

        ret = session->open_cursor(
            session, "table:access", NULL, NULL, &cursor);
        cursor->set_key(cursor, "key");
        cursor->set_value(cursor, "value");
        ret = cursor->insert(cursor);
        ret = cursor->close(cursor);

        ret = session->checkpoint(session, NULL);

        ret = print_database_stats(session);

        ret = print_file_stats(session);

        ret = print_overflow_pages(session);

        ret = print_derived_stats(session);

        return (conn->close(conn, NULL) == 0 ? ret : EXIT_FAILURE);
}