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get_raw_page reads the specified block of the named relation and returns a copy as abytea value. This allows a single time-consistent copy of the block to be obtained.fork should be'main' for the main data fork,'fsm' for the free space map,'vm' for the visibility map, or'init' for the initialization fork.

A shorthand version ofget_raw_page, for reading from the main fork. Equivalent toget_raw_page(relname, 'main', blkno)

page_header shows fields that are common to allPostgres Pro heap and index pages.

A page image obtained withget_raw_page should be passed as argument. For example:

test=# SELECT * FROM page_header(get_raw_page('pg_class', 0));    lsn    | checksum | flags  | lower | upper | special | pagesize | version | prune_xid-----------+----------+--------+-------+-------+---------+----------+---------+----------- 0/24A1B50 |        1 |      1 |   232 |   368 |    8192 |     8192 |       4 |         0

The returned columns correspond to the fields in thePageHeaderData struct. Seesrc/include/storage/bufpage.h for details.

heap_page_items shows all line pointers on a heap page. For those line pointers that are in use, tuple headers as well as tuple raw data are also shown. All tuples are shown, whether or not the tuples were visible to an MVCC snapshot at the time the raw page was copied.

A heap page image obtained withget_raw_page should be passed as argument. For example:

test=# SELECT * FROM heap_page_items(get_raw_page('pg_class', 0));

Seesrc/include/storage/itemid.h andsrc/include/access/htup_details.h for explanations of the fields returned.

tuple_data_split splits tuple data into attributes in the same way as backend internals.

test=# SELECT tuple_data_split('pg_class'::regclass, t_data, t_infomask, t_infomask2, t_bits) FROM heap_page_items(get_raw_page('pg_class', 0));

This function should be called with the same arguments as the return attributes ofheap_page_items.

Ifdo_detoast istrue, attribute that will be detoasted as needed. Default value isfalse.

heap_page_item_attrs is equivalent toheap_page_items except that it returns tuple raw data as an array of attributes that can optionally be detoasted bydo_detoast which isfalse by default.

A heap page image obtained withget_raw_page should be passed as argument. For example:

test=# SELECT * FROM heap_page_item_attrs(get_raw_page('pg_class', 0), 'pg_class'::regclass);

bt_metap returns information about a B-tree index's metapage. For example:

test=# SELECT * FROM bt_metap('pg_cast_oid_index');-[ RECORD 1 ]-----magic     | 340322version   | 2root      | 1level     | 0fastroot  | 1fastlevel | 0

bt_page_stats returns summary information about single pages of B-tree indexes. For example:

test=# SELECT * FROM bt_page_stats('pg_cast_oid_index', 1);-[ RECORD 1 ]-+-----blkno         | 1type          | llive_items    | 256dead_items    | 0avg_item_size | 12page_size     | 8192free_size     | 4056btpo_prev     | 0btpo_next     | 0btpo          | 0btpo_flags    | 3

bt_page_items returns detailed information about all of the items on a B-tree index page. For example:

test=# SELECT * FROM bt_page_items('pg_cast_oid_index', 1); itemoffset |  ctid   | itemlen | nulls | vars |    data------------+---------+---------+-------+------+-------------          1 | (0,1)   |      12 | f     | f    | 23 27 00 00          2 | (0,2)   |      12 | f     | f    | 24 27 00 00          3 | (0,3)   |      12 | f     | f    | 25 27 00 00          4 | (0,4)   |      12 | f     | f    | 26 27 00 00          5 | (0,5)   |      12 | f     | f    | 27 27 00 00          6 | (0,6)   |      12 | f     | f    | 28 27 00 00          7 | (0,7)   |      12 | f     | f    | 29 27 00 00          8 | (0,8)   |      12 | f     | f    | 2a 27 00 00

In a B-tree leaf page,ctid points to a heap tuple. In an internal page, the block number part ofctid points to another page in the index itself, while the offset part (the second number) is ignored and is usually 1.

Note that the first item on any non-rightmost page (any page with a non-zero value in thebtpo_next field) is the page's“high key”, meaning itsdata serves as an upper bound on all items appearing on the page, while itsctid field is meaningless. Also, on non-leaf pages, the first real data item (the first item that is not a high key) is a“minus infinity” item, with no actual value in itsdata field. Such an item does have a valid downlink in itsctid field, however.

brin_page_type returns the page type of the givenBRIN index page, or throws an error if the page is not a validBRIN page. For example:

test=# SELECT brin_page_type(get_raw_page('brinidx', 0)); brin_page_type ---------------- meta

brin_metapage_info returns assorted information about aBRIN index metapage. For example:

test=# SELECT * FROM brin_metapage_info(get_raw_page('brinidx', 0));   magic    | version | pagesperrange | lastrevmappage ------------+---------+---------------+---------------- 0xA8109CFA |       1 |             4 |              2

brin_revmap_data returns the list of tuple identifiers in aBRIN index range map page. For example:

test=# SELECT * FROM brin_revmap_data(get_raw_page('brinidx', 2)) limit 5;  pages  --------- (6,137) (6,138) (6,139) (6,140) (6,141)

brin_page_items returns the data stored in theBRIN data page. For example:

test=# SELECT * FROM brin_page_items(get_raw_page('brinidx', 5),                                     'brinidx')       ORDER BY blknum, attnum LIMIT 6; itemoffset | blknum | attnum | allnulls | hasnulls | placeholder |    value     ------------+--------+--------+----------+----------+-------------+--------------        137 |      0 |      1 | t        | f        | f           |         137 |      0 |      2 | f        | f        | f           | {1 .. 88}        138 |      4 |      1 | t        | f        | f           |         138 |      4 |      2 | f        | f        | f           | {89 .. 176}        139 |      8 |      1 | t        | f        | f           |         139 |      8 |      2 | f        | f        | f           | {177 .. 264}

The returned columns correspond to the fields in theBrinMemTuple andBrinValues structs. Seesrc/include/access/brin_tuple.h for details.

gin_metapage_info returns information about aGIN index metapage. For example:

test=# SELECT * FROM gin_metapage_info(get_raw_page('gin_index', 0));-[ RECORD 1 ]----+-----------pending_head     | 4294967295pending_tail     | 4294967295tail_free_size   | 0n_pending_pages  | 0n_pending_tuples | 0n_total_pages    | 7n_entry_pages    | 6n_data_pages     | 0n_entries        | 693version          | 2

gin_page_opaque_info returns information about aGIN index opaque area, like the page type. For example:

test=# SELECT * FROM gin_page_opaque_info(get_raw_page('gin_index', 2)); rightlink | maxoff |         flags-----------+--------+------------------------         5 |      0 | {data,leaf,compressed}(1 row)

gin_leafpage_items returns information about the data stored in aGIN leaf page. For example:

test=# SELECT first_tid, nbytes, tids[0:5] as some_tids        FROM gin_leafpage_items(get_raw_page('gin_test_idx', 2)); first_tid | nbytes |                        some_tids-----------+--------+---------------------------------------------------------- (8,41)    |    244 | {"(8,41)","(8,43)","(8,44)","(8,45)","(8,46)"} (10,45)   |    248 | {"(10,45)","(10,46)","(10,47)","(10,48)","(10,49)"} (12,52)   |    248 | {"(12,52)","(12,53)","(12,54)","(12,55)","(12,56)"} (14,59)   |    320 | {"(14,59)","(14,60)","(14,61)","(14,62)","(14,63)"} (167,16)  |    376 | {"(167,16)","(167,17)","(167,18)","(167,19)","(167,20)"} (170,30)  |    376 | {"(170,30)","(170,31)","(170,32)","(170,33)","(170,34)"} (173,44)  |    197 | {"(173,44)","(173,45)","(173,46)","(173,47)","(173,48)"}(7 rows)

fsm_page_contents shows the internal node structure of a FSM page. The output is a multiline string, with one line per node in the binary tree within the page. Only those nodes that are not zero are printed. The so-called "next" pointer, which points to the next slot to be returned from the page, is also printed.

Seesrc/backend/storage/freespace/README for more information on the structure of an FSM page.