database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-30 11:03:19 +03:00
Code Activity

Uppercase keywords where appropriate.

Browse Source
This commit is contained in:
Bruce Momjian
2001-10-12 23:32:34 +00:00
parent b57705673d
commit 705869dd17
12 changed files with 212 additions and 219 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
doc/src/sgml/perform.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.11 2001/10/09 18:46:00 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.12 2001/10/12 23:32:34 momjian Exp $
-->
<chapter id="performance-tips">
@ -95,7 +95,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.11 2001/10/09 18:46:00 pet
vacuum analyze, and 7.2 development sources):
<programlisting>
regression=# explain select * from tenk1;
regression=# EXPLAIN SELECT * FROM tenk1;
NOTICE: QUERY PLAN:
Seq Scan on tenk1 (cost=0.00..333.00 rows=10000 width=148)
@ -106,7 +106,7 @@ Seq Scan on tenk1 (cost=0.00..333.00 rows=10000 width=148)
This is about as straightforward as it gets. If you do
<programlisting>
select * from pg_class where relname = 'tenk1';
SELECT * FROM pg_class WHERE relname = 'tenk1';
</programlisting>
you will find out that <classname>tenk1</classname> has 233 disk
@ -119,7 +119,7 @@ select * from pg_class where relname = 'tenk1';
Now let's modify the query to add a qualification clause:
<programlisting>
regression=# explain select * from tenk1 where unique1 &lt; 1000;
regression=# EXPLAIN SELECT * FROM tenk1 WHERE unique1 &lt; 1000;
NOTICE: QUERY PLAN:
Seq Scan on tenk1 (cost=0.00..358.00 rows=1007 width=148)
@ -144,7 +144,7 @@ Seq Scan on tenk1 (cost=0.00..358.00 rows=1007 width=148)
Modify the query to restrict the qualification even more:
<programlisting>
regression=# explain select * from tenk1 where unique1 &lt; 50;
regression=# EXPLAIN SELECT * FROM tenk1 WHERE unique1 &lt; 50;
NOTICE: QUERY PLAN:
Index Scan using tenk1_unique1 on tenk1 (cost=0.00..181.09 rows=49 width=148)
@ -162,7 +162,7 @@ Index Scan using tenk1_unique1 on tenk1 (cost=0.00..181.09 rows=49 width=148)
Add another condition to the qualification:
<programlisting>
regression=# explain select * from tenk1 where unique1 &lt; 50 and
regression=# EXPLAIN SELECT * FROM tenk1 WHERE unique1 &lt; 50 AND
regression-# stringu1 = 'xxx';
NOTICE: QUERY PLAN:
@ -177,8 +177,8 @@ Index Scan using tenk1_unique1 on tenk1 (cost=0.00..181.22 rows=1 width=148)
Let's try joining two tables, using the fields we have been discussing:
<programlisting>
regression=# explain select * from tenk1 t1, tenk2 t2 where t1.unique1 &lt; 50
regression-# and t1.unique2 = t2.unique2;
regression=# EXPLAIN SELECT * FROM tenk1 t1, tenk2 t2 WHERE t1.unique1 &lt; 50
regression-# AND t1.unique2 = t2.unique2;
NOTICE: QUERY PLAN:
Nested Loop (cost=0.00..330.41 rows=49 width=296)
@ -225,8 +225,8 @@ Nested Loop (cost=0.00..330.41 rows=49 width=296)
<programlisting>
regression=# set enable_nestloop = off;
SET VARIABLE
regression=# explain select * from tenk1 t1, tenk2 t2 where t1.unique1 &lt; 50
regression-# and t1.unique2 = t2.unique2;
regression=# EXPLAIN SELECT * FROM tenk1 t1, tenk2 t2 WHERE t1.unique1 &lt; 50
regression-# AND t1.unique2 = t2.unique2;
NOTICE: QUERY PLAN:
Hash Join (cost=181.22..564.83 rows=49 width=296)
@ -257,9 +257,9 @@ Hash Join (cost=181.22..564.83 rows=49 width=296)
For example, we might get a result like this:
<screen>
regression=# explain analyze
regression-# select * from tenk1 t1, tenk2 t2
regression-# where t1.unique1 &lt; 50 and t1.unique2 = t2.unique2;
regression=# EXPLAIN ANALYZE
regression-# SELECT * FROM tenk1 t1, tenk2 t2
regression-# WHERE t1.unique1 &lt; 50 AND t1.unique2 = t2.unique2;
NOTICE: QUERY PLAN:
Nested Loop (cost=0.00..330.41 rows=49 width=296) (actual time=1.31..28.90 rows=50 loops=1)