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Rewrite of planner statistics-gathering code. ANALYZE is now available as

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a separate statement (though it can still be invoked as part of VACUUM, too).
pg_statistic redesigned to be more flexible about what statistics are
stored.  ANALYZE now collects a list of several of the most common values,
not just one, plus a histogram (not just the min and max values).  Random
sampling is used to make the process reasonably fast even on very large
tables.  The number of values and histogram bins collected is now
user-settable via an ALTER TABLE command.

There is more still to do; the new stats are not being used everywhere
they could be in the planner.  But the remaining changes for this project
should be localized, and the behavior is already better than before.

A not-very-related change is that sorting now makes use of btree comparison
routines if it can find one, rather than invoking '<' twice.
This commit is contained in:
Tom Lane
2001-05-07 00:43:27 +00:00
parent 9583aea9d0
commit f905d65ee3
66 changed files with 4131 additions and 2063 deletions
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26
doc/src/sgml/ref/alter_table.sgml
View File

@@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.22 2001/03/05 18:42:55 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.23 2001/05/07 00:43:15 tgl Exp $
Postgres documentation
-->
@@ -29,7 +29,9 @@ ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> { SET DEFAULT <replaceable
class="PARAMETER">value</replaceable> | DROP DEFAULT }
ALTER TABLE <replaceable class="PARAMETER">table</replaceable> [ * ]
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> SET STATISTICS <replaceable class="PARAMETER">integer</replaceable>
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
RENAME [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> TO <replaceable
class="PARAMETER">newcolumn</replaceable>
ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
@@ -159,9 +161,14 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
<command>ALTER TABLE</command> changes the definition of an existing table.
The <literal>ADD COLUMN</literal> form adds a new column to the table
using the same syntax as <xref linkend="SQL-CREATETABLE"
endterm="SQL-CREATETABLE-title">. The <literal>ALTER COLUMN</literal> form
allows you to set or remove the default for the column. Note that defaults
only apply to newly inserted rows.
endterm="SQL-CREATETABLE-title">.
The <literal>ALTER COLUMN SET/DROP DEFAULT</literal> forms
allow you to set or remove the default for the column. Note that defaults
only apply to subsequent <command>INSERT</command> commands; they do not
cause rows already in the table to change.
The <literal>ALTER COLUMN SET STATISTICS</literal> form allows you to
set the statistics-gathering target for subsequent
<xref linkend="sql-analyze" endterm="sql-analyze-title"> operations.
The <literal>RENAME</literal> clause causes the name of a table or column
to change without changing any of the data contained in
the affected table. Thus, the table or column will
@@ -170,7 +177,7 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
The ADD <replaceable class="PARAMETER">table constraint definition</replaceable> clause
adds a new constraint to the table using the same syntax as <xref
linkend="SQL-CREATETABLE" endterm="SQL-CREATETABLE-title">.
The OWNER clause chnages the owner of the table to the user <replaceable class="PARAMETER">
The OWNER clause changes the owner of the table to the user <replaceable class="PARAMETER">
new user</replaceable>.
</para>
@@ -190,10 +197,11 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
</para>
<para>
In the current implementation, default and constraint clauses for the
In the current implementation of <literal>ADD COLUMN</literal>,
default and constraint clauses for the
new column will be ignored. You can use the <literal>SET DEFAULT</literal>
form of <command>ALTER TABLE</command> to set the default later.
(You will also have to update the already existing rows to the
(You may also want to update the already existing rows to the
new default value, using <xref linkend="sql-update"
endterm="sql-update-title">.)
</para>
@@ -210,7 +218,7 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
<para>
You must own the table in order to change it.
Renaming any part of the schema of a system
Changing any part of the schema of a system
catalog is not permitted.
The <citetitle>PostgreSQL User's Guide</citetitle> has further
information on inheritance.