Question

currently we using MySQL.

We have table with spatial index (so no InnoDB) and doing whole table updates every x seconds (moving object from one place to other).

currently we doing:

UPDATE LOW_PRIORITY IGNORE `table`
SET `column1` = CASE `column2`
              WHEN 1 THEN ...
              WHEN 2 THEN ...
              WHEN 3 THEN ...
              ...
              ELSE `column1`
              END;

but it gets extremely painful as rows number increases. Is there is better way to do entire table updates? Maybe we should switch to other DB (PostGIS, NoSQL)?

Any thoughts on that?

Answer 1

The best way to UPDATE many rows at once is :

• CREATE TEMP TABLE
• Fill it with (primary key, new values) with a big INSERT
• UPDATE table JOIN temptable USING (primary key) SET table.oldvalue=temptable.newvalue

Update :

create table test ( id integer primary key, p point not null );
insert into test (id,p) select id, POINT( id%100, floor(id/100) ) from serie limit 10000;
alter table test add spatial index spi (p);
select id, AsText(p) from test;

+----+-------------+
| id | AsText(p)   |
+----+-------------+
|  1 | POINT(1 0)  |
|  2 | POINT(2 0)  |
|  3 | POINT(3 0)  |
...

|  98 | POINT(98 0) |
|  99 | POINT(99 0) |
| 100 | POINT(0 1)  |
| 101 | POINT(1 1)  |
...

|  9999 | POINT(99 99) |
| 10000 | POINT(0 100) |
+-------+--------------+


EXPLAIN SELECT id,AsText(p) from test where Contains( GeomFromText('POLYGON((0 0,0 10,10 10,10 0,0 0))'), p );
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
|  1 | SIMPLE      | test  | range | spi           | spi  | 34      | NULL |  112 | Using where |
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+

create temporary table test2 ( id integer primary key, p point not null );
insert into test2 (id,p) select id, POINT( 1+(id%100), 1+floor(id/100) ) from serie limit 10000;
update test, test2 set test.p=test2.p where test.id=test2.id;

EXPLAIN SELECT id,AsText(p) from test where Contains( GeomFromText('POLYGON((0 0,0 10,10 10,10 0,0 0))'), p );
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+
|  1 | SIMPLE      | test  | range | spi           | spi  | 34      | NULL |  102 | Using where |
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+

No problem here (MySQL 5.1.41)