Commit c470d5e4 authored by Satya B's avatar Satya B

Applying InnoDB snashot 5.1-ss4699, part 3. Fixes BUG#43660

1) BUG#43660 - SHOW INDEXES/ANALYZE does NOT update cardinality 
               for indexes of InnoDB table

Detailed revision comments:

r4699 | vasil | 2009-04-09 14:01:52 +0300 (Thu, 09 Apr 2009) | 15 lines
branches/5.1:

Fix Bug#43660 SHOW INDEXES/ANALYZE does NOT update cardinality for indexes
of InnoDB table

by replacing the PRNG that is used to pick random pages with a better
one.

This is based on r4670 but also adds a new configuration option and
enables the fix only if this option is changed. Please skip the present
revision when merging.

Approved by:	Heikki (via email)
parent 16c74505
......@@ -8260,6 +8260,14 @@ static MYSQL_SYSVAR_BOOL(stats_on_metadata, innobase_stats_on_metadata,
"Enable statistics gathering for metadata commands such as SHOW TABLE STATUS (on by default)",
NULL, NULL, TRUE);
static MYSQL_SYSVAR_BOOL(use_legacy_cardinality_algorithm,
srv_use_legacy_cardinality_algorithm,
PLUGIN_VAR_OPCMDARG,
"Use legacy algorithm for picking random pages during index cardinality "
"estimation. Disable this to use a better algorithm, but note that your "
"query plans may change (enabled by default).",
NULL, NULL, TRUE);
static MYSQL_SYSVAR_BOOL(adaptive_hash_index, innobase_adaptive_hash_index,
PLUGIN_VAR_OPCMDARG | PLUGIN_VAR_READONLY,
"Enable InnoDB adaptive hash index (enabled by default). "
......@@ -8395,6 +8403,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
MYSQL_SYSVAR(open_files),
MYSQL_SYSVAR(rollback_on_timeout),
MYSQL_SYSVAR(stats_on_metadata),
MYSQL_SYSVAR(use_legacy_cardinality_algorithm),
MYSQL_SYSVAR(adaptive_hash_index),
MYSQL_SYSVAR(status_file),
MYSQL_SYSVAR(support_xa),
......
......@@ -235,6 +235,12 @@ extern ulint srv_read_ahead_seq;
/* variable to count the number of random read-aheads were done */
extern ulint srv_read_ahead_rnd;
/* An option to enable the fix for "Bug#43660 SHOW INDEXES/ANALYZE does
NOT update cardinality for indexes of InnoDB table". By default we are
running with the fix disabled because MySQL 5.1 is frozen for such
behavioral changes. */
extern char srv_use_legacy_cardinality_algorithm;
/* In this structure we store status variables to be passed to MySQL */
typedef struct export_var_struct export_struc;
......
......@@ -15,6 +15,8 @@ Created 10/4/1994 Heikki Tuuri
#include "mtr0log.h"
#include "log0recv.h"
#include "rem0cmp.h"
#include "srv0srv.h"
#include "ut0ut.h"
static ulint page_rnd = 976722341;
......@@ -23,6 +25,44 @@ static ulint page_rnd = 976722341;
ulint page_cur_short_succ = 0;
# endif /* UNIV_SEARCH_PERF_STAT */
/***********************************************************************
This is a linear congruential generator PRNG. Returns a pseudo random
number between 0 and 2^64-1 inclusive. The formula and the constants
being used are:
X[n+1] = (a * X[n] + c) mod m
where:
X[0] = ut_usectime()
a = 1103515245 (3^5 * 5 * 7 * 129749)
c = 12345 (3 * 5 * 823)
m = 18446744073709551616 (2^64)
*/
#define LCG_a 1103515245
#define LCG_c 12345
static
unsigned long long
page_cur_lcg_prng()
/*===============*/
/* out: number between 0 and 2^64-1 */
{
static unsigned long long lcg_current = 0;
static ibool initialized = FALSE;
ulint time_sec;
ulint time_ms;
if (!initialized) {
ut_usectime(&time_sec, &time_ms);
lcg_current = (unsigned long long) (time_sec * 1000000
+ time_ms);
initialized = TRUE;
}
/* no need to "% 2^64" explicitly because lcg_current is
64 bit and this will be done anyway */
lcg_current = LCG_a * lcg_current + LCG_c;
return(lcg_current);
}
/********************************************************************
Tries a search shortcut based on the last insert. */
UNIV_INLINE
......@@ -493,9 +533,13 @@ page_cur_open_on_rnd_user_rec(
return;
}
page_rnd += 87584577;
if (srv_use_legacy_cardinality_algorithm) {
page_rnd += 87584577;
rnd = page_rnd % page_get_n_recs(page);
rnd = page_rnd % page_get_n_recs(page);
} else {
rnd = (ulint) page_cur_lcg_prng() % page_get_n_recs(page);
}
rec = page_get_infimum_rec(page);
......@@ -1437,3 +1481,30 @@ page_cur_delete_rec(
page_dir_balance_slot(page, cur_slot_no);
}
}
#ifdef UNIV_COMPILE_TEST_FUNCS
/***********************************************************************
Print the first n numbers, generated by page_cur_lcg_prng() to make sure
(visually) that it works properly. */
void
test_page_cur_lcg_prng(
/*===================*/
int n) /* in: print first n numbers */
{
int i;
unsigned long long rnd;
for (i = 0; i < n; i++) {
rnd = page_cur_lcg_prng();
printf("%llu\t%%2=%llu %%3=%llu %%5=%llu %%7=%llu %%11=%llu\n",
rnd,
rnd % 2,
rnd % 3,
rnd % 5,
rnd % 7,
rnd % 11);
}
}
#endif /* UNIV_COMPILE_TEST_FUNCS */
......@@ -256,6 +256,12 @@ ulint srv_read_ahead_seq = 0;
/* variable to count the number of random read-aheads */
ulint srv_read_ahead_rnd = 0;
/* An option to enable the fix for "Bug#43660 SHOW INDEXES/ANALYZE does
NOT update cardinality for indexes of InnoDB table". By default we are
running with the fix disabled because MySQL 5.1 is frozen for such
behavioral changes. */
char srv_use_legacy_cardinality_algorithm = TRUE;
/* structure to pass status variables to MySQL */
export_struc export_vars;
......
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