Gevel contrib module provides several functions useful for analyzing GiST and GIN index.

• Online version of this document: http://www.sai.msu.su/~megera/oddmuse/index.cgi/Gevel
• Canonical git repository: git://sigaev.ru/gevel

Caution: This module was designed for advanced users of GIN, GiST and SP-GiST indices !

Authors

* Oleg Bartunov <oleg@sai.msu.su>, Moscow, Moscow University, Russia
* Teodor Sigaev <teodor@sigaev.ru>, Moscow, Moscow University, Russia
* Daria Lepikhova <d.lepikhova@postgrespro.ru>, Postgres Pro

License

Stable version, included into PostgreSQL distribution, released under BSD license. Development version, available from this site, released under the GNU General Public License, version 2 (June 1991)

Install gevel module (requires 8.1+ version): % cd PGSQLSRC/contrib % tar xzvf gevel.tar.gz % make % make install % make installcheck % psql regression < gevel.sql

* gist_stat(INDEXNAME) - show some statistics about GiST tree 

regression=# select gist_stat('pix'); Number of levels: 2 Number of pages: 30 Number of leaf pages: 29 Number of tuples: 3129 Number of leaf tuples: 3100 Total size of tuples: 137676 bytes Total size of leaf tuples: 136400 bytes Total size of index: 245760 bytes

* gist_tree(INDEXNAME[,MAXLEVEL]) - show GiST tree up to MAXLEVEL 

regression=# select gist_tree('pix',0); 0(l:0) blk: 0 numTuple: 29 free: 6888b(15.63%)

Designation (from left to right):

      o 0 - page number
      o (l:0) - tree level
      o blk: 0 - block number
      o numTuple: 29 - the number of tuples
      o free: 6888b - free space in bytes
      o (15.63%) - occupied space in percents

* gist_tree(INDEXNAME) - show full GiST tree 

regression=# select gist_tree('pix'); 0(l:0) blk: 0 numTuple: 29 free: 6888b(15.63%) 1(l:1) blk: 13 numTuple: 180 free: 244b(97.01%) 2(l:1) blk: 11 numTuple: 175 free: 464b(94.32%) 3(l:1) blk: 2 numTuple: 101 free: 3720b(54.43%) 4(l:1) blk: 17 numTuple: 111 free: 3280b(59.82%) 5(l:1) blk: 18 numTuple: 101 free: 3720b(54.43%) 6(l:1) blk: 10 numTuple: 98 free: 3852b(52.82%) 7(l:1) blk: 19 numTuple: 111 free: 3280b(59.82%) 8(l:1) blk: 9 numTuple: 97 free: 3896b(52.28%) 9(l:1) blk: 20 numTuple: 104 free: 3588b(56.05%) 10(l:1) blk: 14 numTuple: 96 free: 3940b(51.74%) 11(l:1) blk: 21 numTuple: 106 free: 3500b(57.13%) 12(l:1) blk: 7 numTuple: 103 free: 3632b(55.51%) 13(l:1) blk: 1 numTuple: 101 free: 3720b(54.43%) 14(l:1) blk: 16 numTuple: 97 free: 3896b(52.28%) 15(l:1) blk: 24 numTuple: 103 free: 3632b(55.51%) 16(l:1) blk: 4 numTuple: 98 free: 3852b(52.82%) 17(l:1) blk: 25 numTuple: 98 free: 3852b(52.82%) 18(l:1) blk: 3 numTuple: 97 free: 3896b(52.28%) 19(l:1) blk: 26 numTuple: 96 free: 3940b(51.74%) 20(l:1) blk: 6 numTuple: 103 free: 3632b(55.51%) 21(l:1) blk: 8 numTuple: 162 free: 1036b(87.31%) 22(l:1) blk: 23 numTuple: 94 free: 4028b(50.66%) 23(l:1) blk: 12 numTuple: 82 free: 4556b(44.19%) 24(l:1) blk: 27 numTuple: 105 free: 3544b(56.59%) 25(l:1) blk: 5 numTuple: 90 free: 4204b(48.51%) 26(l:1) blk: 28 numTuple: 100 free: 3764b(53.90%) 27(l:1) blk: 22 numTuple: 101 free: 3720b(54.43%) 28(l:1) blk: 15 numTuple: 95 free: 3984b(51.20%) 29(l:1) blk: 29 numTuple: 95 free: 3984b(51.20%)

* gist_print(INDEXNAME) - prints objects stored in GiST tree, 
 works only if objects in index have textual representation 
 (type_out functions should be implemented for given object type). 
 It's known to work with R-tree GiST based index. 
 Note, in example below, objects are of type box. 

select * from gist_print('pix') as t(level int, valid bool, a box) where level =1;

level | valid | a -------+-------+----------------------------- 1 | t | (37357,50073),(34242,357) 1 | t | (43499,49770),(40358,43) 1 | t | (31193,24679),(25047,12410) 1 | t | (31018,12142),(25083,6) 1 | t | (49944,25174),(43471,12802) 1 | t | (12577,49757),(6302,37534) 1 | t | (12528,37333),(6171,24861) 1 | t | (50027,49751),(46817,25462) 1 | t | (46870,49912),(43664,25722) 1 | t | (24855,25574),(12447,19263) 1 | t | (25054,19126),(12403,12796) 1 | t | (32737,49923),(31178,1038) 1 | t | (3184,24465),(15,81) 1 | t | (24951,49983),(12740,44000) 1 | t | (24919,43956),(12617,37901) 1 | t | (40387,49852),(37338,25217) 1 | t | (40325,24963),(37375,491) 1 | t | (24919,12698),(12654,6518) 1 | t | (25002,6338),(12350,51) 1 | t | (49985,12554),(43447,222) 1 | t | (25003,37769),(12552,25573) 1 | t | (34270,49382),(32763,594) 1 | t | (6205,50012),(3,37527) 1 | t | (6163,37358),(120,25034) 1 | t | (12343,24542),(9295,294) 1 | t | (9308,24151),(6234,620) 1 | t | (6230,24629),(3169,108) 1 | t | (31179,50040),(28113,25556) 1 | t | (28048,49694),(25000,25000) (29 rows)

* spgist_stat(INDEXNAME) - show some statistics about SP-GiST tree

SELECT spgist_stat('spgist_idx');

       spgist_stat            

---

totalPages: 21 + deletedPages: 0 + innerPages: 3 + leafPages: 18 + emptyPages: 1 + usedSpace: 121.27 kbytes+ freeSpace: 46.07 kbytes + fillRatio: 72.47% + leafTuples: 3669 + innerTuples: 20 + innerAllTheSame: 0 + leafPlaceholders: 569 + innerPlaceholders: 0 + leafRedirects: 0 + innerRedirects: 0

* spgist_print(INDEXNAME) - prints objects stored in GiST tree, 
 works only if objects in index have textual representation 
 (type_out functions should be implemented for given object type).
 Note 1. in example below we used quad_point_ops which uses point
	for leaf and prefix value, but doesn't use node_label at all.
	Use type  'int' as dummy type for prefix or/and node_label.
 Note 2
	quad_point_ops: prefix point, node_label int,  leaf_value point
	kd_point_ops:   prefix float, node_label int,  leaf_value point
	text_ops:       prefix text,  node_label char, leaf_value text

SELECT * FROM spgist_print('spgist_idx') as t

	(
		tid tid,
		allthesame bool,
		node_n int, 
		level int, 
		tid_pointer tid, 
		prefix point, 
		node_label int, 
		leaf_value point
	) where level = 1;

tid | allthesame | node_n | level | tid_pointer | prefix | node_label | leaf_value -------+------------+--------+-------+-------------+-------------------------------------+------------+------------ (1,1) | f | 0 | 1 | (5,4) | (24530.2070484581,23595.7092511013) | | (1,1) | f | 1 | 1 | (5,3) | (24530.2070484581,23595.7092511013) | | (1,1) | f | 2 | 1 | (5,2) | (24530.2070484581,23595.7092511013) | | (1,1) | f | 3 | 1 | (5,1) | (24530.2070484581,23595.7092511013) | |

• gin_stat(INDEXNAME) prints estimated counts for each indexed values Note: since 8.4 gin_stat function has gin_stat(INDEXNAME, COLNUMBER) prototype, single-argument function will return result for a first column of index

SELECT * FROM gin_stat('gin_idx') as t(value int, nrow int) where nrow > 250;

value | nrow -------+------ 31 | 254 47 | 251 52 | 257 59 | 259 (4 rows)

• bigint gin_count_estimate(INDEXNAME, TSQUERY) outputs number of indexed rows matched query. It doesn't touch heap at all.

select gin_count_estimate('qq', 'star');

gin_count_estimate

			 790

(1 row)

• text gin_statpage(INDEXNAME) Prints various stat about index internals.

select gin_statpage('gin_idx');

     gin_statpage         

---

totalPages: 32 + dataPages: 1 + dataInnerPages: 0 + dataLeafPages: 1 + dataInnerFreeSpace: 0 + dataLeafFreeSpace: 4454 + dataInnerTuplesCount: 0 + dataLeafIptrsCount: 3600 + entryPages: 31 + entryInnerPages: 21 + entryLeafPages: 10 + entryInnerFreeSpace: 15160+ entryLeafFreeSpace: 32788+ entryInnerTuplesCount: 7810 + entryLeafTuplesCount: 305 + entryPostingSize: 42122+ entryPostingCount: 96759+ entryAttrSize: 64924+

• btree_stat(INDEXNAME) - show some statistics about btree index

SELECT btree_stat('btree_idx');

     btree_stat                

---

Number of levels: 2 + Number of pages: 75 + Number of leaf pages: 74 + Number of tuples: 11047 + Number of invalid tuples: 0 + Number of leaf tuples: 10973 + Total size of tuples: 547824 bytes+ Total size of leaf tuples: 543948 bytes+ Total size of index: 614400 bytes+

(1 row)

• btree_tree(INDEXNAME[, MAXLEVEL]) - show btree elements from root up to MAXLEVEL

SELECT btree_tree('btree_idx');

                     btree_tree            

---

lvl: 0, blk: 3, numTuples: 74 + lvl: 1, blk: 1, numTuples: 139 + lvl: 1, blk: 2, numTuples: 139 + lvl: 1, blk: 4, numTuples: 139 + lvl: 1, blk: 5, numTuples: 136 + lvl: 1, blk: 6, numTuples: 141 + lvl: 1, blk: 7, numTuples: 139 + lvl: 1, blk: 8, numTuples: 140 + lvl: 1, blk: 9, numTuples: 136 + lvl: 1, blk: 10, numTuples: 140+ lvl: 1, blk: 11, numTuples: 138+ lvl: 1, blk: 12, numTuples: 143+ lvl: 1, blk: 13, numTuples: 137+ lvl: 1, blk: 14, numTuples: 138+ lvl: 1, blk: 15, numTuples: 140+ lvl: 1, blk: 16, numTuples: 141+