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| -rw-r--r-- | doc/src/sgml/perform.sgml | 27 |
1 files changed, 21 insertions, 6 deletions
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml index bd93cb0dd2e..a2f7e0629f7 100644 --- a/doc/src/sgml/perform.sgml +++ b/doc/src/sgml/perform.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/perform.sgml,v 1.77 2010/04/28 16:10:40 heikki Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/perform.sgml,v 1.78 2010/04/28 16:48:21 alvherre Exp $ --> <chapter id="performance-tips"> <title>Performance Tips</title> @@ -554,16 +554,31 @@ WHERE relname LIKE 'tenk1%'; For example, we might do: <screen> -SELECT attname, n_distinct, most_common_vals +SELECT attname, inherited, n_distinct, + array_to_string(most_common_vals, E'\n') as most_common_vals FROM pg_stats WHERE tablename = 'road'; - attname | n_distinct | most_common_vals ----------+------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - name | -0.467008 | {"I- 580 Ramp","I- 880 Ramp","Sp Railroad ","I- 580 ","I- 680 Ramp","I- 80 Ramp","14th St ","5th St ","Mission Blvd","I- 880 "} - thepath | 20 | {"[(-122.089,37.71),(-122.0886,37.711)]"} + attname | inherited | n_distinct | most_common_vals +---------+-----------+------------+------------------------------------ + name | f | -0.363388 | I- 580 Ramp+ + | | | I- 880 Ramp+ + | | | Sp Railroad + + | | | I- 580 + + | | | I- 680 Ramp + name | t | -0.284859 | I- 880 Ramp+ + | | | I- 580 Ramp+ + | | | I- 680 Ramp+ + | | | I- 580 + + | | | State Hwy 13 Ramp (2 rows) </screen> + + Note that two rows are displayed for the same column, one corresponding + to the complete inheritance hierarchy starting at the + <literal>road</literal> table (<literal>inherited</>=<literal>t</>), + and another one including only the <literal>road</literal> table itself + (<literal>inherited</>=<literal>f</>). </para> <para> |