Hi all,
I have a simple Table on a one node cluster.
Have filled it with 100mil lines of random data.
but i dont understand why a
select count(*) from people; is 20 times faster than a
select count(id) from people; where id is indexed
is there a reason for this?
below table structure and explains
#### 8.246 seconds execution time
0: jdbc:ignite:thin://127.0.0.1/> select count(*) from people;
+--------------------------------+
| COUNT(*) |
+--------------------------------+
| 99993600 |
+--------------------------------+
1 row selected (8.246 seconds)
0: jdbc:ignite:thin://127.0.0.1/> explain select count(*) from people;
+--------------------------------+
| PLAN |
+--------------------------------+
| SELECT
COUNT(*) AS __C0_0
FROM PUBLIC.PEOPLE __Z0
/* PUBLIC.PEOPLE.__SCAN_ */
/* direct lookup */ |
| SELECT
CAST(SUM(__C0_0) AS BIGINT) AS __C0_0
FROM PUBLIC.__T0
/* PUBLIC."merge_scan" */ |
+--------------------------------+
2 rows selected (0.005 seconds)
#### 136.719 seconds executin time
0: jdbc:ignite:thin://127.0.0.1/> select count(id) from people;
+--------------------------------+
| COUNT(ID) |
+--------------------------------+
| 99993600 |
+--------------------------------+
1 row selected (136.719 seconds)
explain select count(id) from people;
+--------------------------------+
| PLAN |
+--------------------------------+
| SELECT
COUNT(__Z0.ID) AS __C0_0
FROM PUBLIC.PEOPLE __Z0
/* PUBLIC."_key_PK_proxy" */ |
| SELECT
CAST(SUM(__C0_0) AS BIGINT) AS __C0_0
FROM PUBLIC.__T0
/* PUBLIC."merge_scan" */ |
+--------------------------------+
2 rows selected (0.004 seconds)
sql = "CREATE TABLE IF NOT EXISTS People " +
"(id BIGINT, " +
"first_name varchar(20), " +
"last_name varchar(20), " +
"age int, " +
"current_city_id int, " +
"born_city_id int, " +
"gender varchar(1), " +
"PRIMARY KEY(id)) " +
"WITH \"template=PARTITIONED\""
--
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