Version 3.1.1
ex_stat.c

Shows how to access database and table statistics.

/*-
* Public Domain 2014-2018 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 <test_util.h>
void get_stat(WT_CURSOR *cursor, int stat_field, uint64_t *valuep);
void print_cursor(WT_CURSOR *);
void print_database_stats(WT_SESSION *);
void print_derived_stats(WT_SESSION *);
void print_file_stats(WT_SESSION *);
void print_join_cursor_stats(WT_SESSION *);
void print_overflow_pages(WT_SESSION *);
static const char *home;
void
print_cursor(WT_CURSOR *cursor)
{
const char *desc, *pvalue;
uint64_t value;
int ret;
while ((ret = cursor->next(cursor)) == 0) {
error_check(cursor->get_value(cursor, &desc, &pvalue, &value));
if (value != 0)
printf("%s=%s\n", desc, pvalue);
}
scan_end_check(ret == WT_NOTFOUND);
}
void
print_database_stats(WT_SESSION *session)
{
WT_CURSOR *cursor;
error_check(session->open_cursor(
session, "statistics:", NULL, NULL, &cursor));
print_cursor(cursor);
error_check(cursor->close(cursor));
}
void
print_file_stats(WT_SESSION *session)
{
WT_CURSOR *cursor;
error_check(session->open_cursor(
session, "statistics:table:access", NULL, NULL, &cursor));
print_cursor(cursor);
error_check(cursor->close(cursor));
}
void
print_join_cursor_stats(WT_SESSION *session)
{
WT_CURSOR *idx_cursor, *join_cursor, *stat_cursor;
error_check(session->create(
session, "index:access:idx", "columns=(v)"));
error_check(session->open_cursor(
session, "index:access:idx", NULL, NULL, &idx_cursor));
error_check(idx_cursor->next(idx_cursor));
error_check(session->open_cursor(
session, "join:table:access", NULL, NULL, &join_cursor));
error_check(session->join(
session, join_cursor, idx_cursor, "compare=gt"));
print_cursor(join_cursor);
error_check(session->open_cursor(session,
"statistics:join", join_cursor, NULL, &stat_cursor));
print_cursor(stat_cursor);
error_check(stat_cursor->close(stat_cursor));
error_check(join_cursor->close(join_cursor));
error_check(idx_cursor->close(idx_cursor));
}
void
print_overflow_pages(WT_SESSION *session)
{
WT_CURSOR *cursor;
const char *desc, *pvalue;
uint64_t value;
error_check(session->open_cursor(session,
"statistics:table:access", NULL, NULL, &cursor));
error_check(cursor->search(cursor));
error_check(cursor->get_value(cursor, &desc, &pvalue, &value));
printf("%s=%s\n", desc, pvalue);
error_check(cursor->close(cursor));
}
void
get_stat(WT_CURSOR *cursor, int stat_field, uint64_t *valuep)
{
const char *desc, *pvalue;
cursor->set_key(cursor, stat_field);
error_check(cursor->search(cursor));
error_check(cursor->get_value(cursor, &desc, &pvalue, valuep));
}
void
print_derived_stats(WT_SESSION *session)
{
WT_CURSOR *cursor;
error_check(session->open_cursor(session,
"statistics:table:access", NULL, NULL, &cursor));
{
uint64_t ckpt_size, file_size, percent;
get_stat(cursor, WT_STAT_DSRC_BLOCK_CHECKPOINT_SIZE, &ckpt_size);
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;
get_stat(cursor, WT_STAT_DSRC_CURSOR_INSERT_BYTES, &app_insert);
get_stat(cursor, WT_STAT_DSRC_CURSOR_REMOVE_BYTES, &app_remove);
get_stat(cursor, WT_STAT_DSRC_CURSOR_UPDATE_BYTES, &app_update);
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));
}
error_check(cursor->close(cursor));
}
int
main(int argc, char *argv[])
{
WT_CURSOR *cursor;
WT_SESSION *session;
home = example_setup(argc, argv);
error_check(
wiredtiger_open(home, NULL, "create,statistics=(all)", &conn));
error_check(conn->open_session(conn, NULL, NULL, &session));
error_check(session->create(session,
"table:access", "key_format=S,value_format=S,columns=(k,v)"));
error_check(session->open_cursor(
session, "table:access", NULL, NULL, &cursor));
cursor->set_key(cursor, "key");
cursor->set_value(cursor, "value");
error_check(cursor->insert(cursor));
error_check(cursor->close(cursor));
error_check(session->checkpoint(session, NULL));
print_database_stats(session);
print_file_stats(session);
print_join_cursor_stats(session);
print_overflow_pages(session);
print_derived_stats(session);
error_check(conn->close(conn, NULL));
return (EXIT_SUCCESS);
}