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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/src/sgml/pageinspect.sgml | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/doc/src/sgml/pageinspect.sgml b/doc/src/sgml/pageinspect.sgml index d12dbac32db..4c201e75b0d 100644 --- a/doc/src/sgml/pageinspect.sgml +++ b/doc/src/sgml/pageinspect.sgml @@ -493,4 +493,148 @@ test=# SELECT first_tid, nbytes, tids[0:5] AS some_tids </variablelist> </sect2> + <sect2> + <title>Hash Functions</title> + + <variablelist> + <varlistentry> + <term> + <function>hash_page_type(page bytea) returns text</function> + <indexterm> + <primary>hash_page_type</primary> + </indexterm> + </term> + + <listitem> + <para> + <function>hash_page_type</function> returns page type of + the given <acronym>HASH</acronym> index page. For example: +<screen> +test=# SELECT hash_page_type(get_raw_page('con_hash_index', 0)); + hash_page_type +---------------- + metapage +</screen> + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term> + <function>hash_page_stats(page bytea) returns setof record</function> + <indexterm> + <primary>hash_page_stats</primary> + </indexterm> + </term> + + <listitem> + <para> + <function>hash_page_stats</function> returns information about + a bucket or overflow page of a <acronym>HASH</acronym> index. + For example: +<screen> +test=# SELECT * FROM hash_page_stats(get_raw_page('con_hash_index', 1)); +-[ RECORD 1 ]---+----------- +live_items | 407 +dead_items | 0 +page_size | 8192 +free_size | 8 +hasho_prevblkno | 4294967295 +hasho_nextblkno | 8474 +hasho_bucket | 0 +hasho_flag | 66 +hasho_page_id | 65408 +</screen> + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term> + <function>hash_page_items(page bytea) returns setof record</function> + <indexterm> + <primary>hash_page_items</primary> + </indexterm> + </term> + + <listitem> + <para> + <function>hash_page_items</function> returns information about + the data stored in a bucket or overflow page of a <acronym>HASH</acronym> + index page. For example: +<screen> +test=# SELECT * FROM hash_page_items(get_raw_page('con_hash_index', 1)) LIMIT 5; + itemoffset | ctid | data +------------+-----------+------------ + 1 | (899,77) | 1053474816 + 2 | (897,29) | 1053474816 + 3 | (894,207) | 1053474816 + 4 | (892,159) | 1053474816 + 5 | (890,111) | 1053474816 +</screen> + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term> + <function>hash_bitmap_info(index oid, blkno int) returns record</function> + <indexterm> + <primary>hash_bitmap_info</primary> + </indexterm> + </term> + + <listitem> + <para> + <function>hash_bitmap_info</function> shows the status of a bit + in the bitmap page for a particular overflow page of <acronym>HASH</acronym> + index. For example: +<screen> +test=# SELECT * FROM hash_bitmap_info('con_hash_index', 2052); + bitmapblkno | bitmapbit | bitstatus +-------------+-----------+----------- + 65 | 3 | t +</screen> + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term> + <function>hash_metapage_info(page bytea) returns record</function> + <indexterm> + <primary>hash_metapage_info</primary> + </indexterm> + </term> + + <listitem> + <para> + <function>hash_metapage_info</function> returns information stored + in meta page of a <acronym>HASH</acronym> index. For example: +<screen> +test=# SELECT * FROM hash_metapage_info(get_raw_page('con_hash_index', 0)); +-[ RECORD 1 ]----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- +magic | 105121344 +version | 2 +ntuples | 500500 +ffactor | 40 +bsize | 8152 +bmsize | 4096 +bmshift | 15 +maxbucket | 12512 +highmask | 16383 +lowmask | 8191 +ovflpoint | 14 +firstfree | 1204 +nmaps | 1 +procid | 450 +spares | {0,0,0,0,0,0,1,1,1,1,1,4,59,704,1204,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} +mapp | {65,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} +</screen> + </para> + </listitem> + </varlistentry> + </variablelist> + </sect2> + </sect1> |