Hi, I'm chasing an apparent index corruption problem, and I came across something I can't quite explain in pg_filedump. Say I dump a non-leaf btree index page:
******************************************************************* * PostgreSQL File/Block Formatted Dump Utility - Version 8.3.0 * * File: 31141 * Options used: -fi -x -R 6246 * * Dump created on: Tue Apr 6 17:40:28 2010 ******************************************************************* Block 6246 ******************************************************** <Header> ----- Block Offset: 0x030cc000 Offsets: Lower 36 (0x0024) Block: Size 8192 Version 4 Upper 8120 (0x1fb8) LSN: logid 1077 recoff 0x45c8b660 Special 8176 (0x1ff0) Items: 3 Free Space: 8084 TLI: 0x0001 Prune XID: 0x00000000 Flags: 0x0000 () Length (including item array): 36 0000: 35040000 60b6c845 01000000 2400b81f 5...`..E....$... 0010: f01f0420 00000000 d89f3000 d09f1000 ... ......0..... 0020: b89f3000 ..0. <Data> ------ Item 1 -- Length: 24 Offset: 8152 (0x1fd8) Flags: NORMAL Block Id: 6232 linp Index: 1 Size: 24 Has Nulls: 32768 Has Varwidths: 0 1fd8: 00005818 01001880 01000000 00000000 ..X............. 1fe8: 80bcc57d 74230100 ...}t#.. Item 2 -- Length: 8 Offset: 8144 (0x1fd0) Flags: NORMAL Block Id: 2756 linp Index: 1 Size: 8 Has Nulls: 0 Has Varwidths: 0 1fd0: 0000c40a 01000800 ........ Item 3 -- Length: 24 Offset: 8120 (0x1fb8) Flags: NORMAL Block Id: 6231 linp Index: 1 Size: 24 Has Nulls: 32768 Has Varwidths: 0 1fb8: 00005718 01001880 01000000 00000000 ..W............. 1fc8: 4009cc7f 73230100 @...s#.. <Special Section> ----- BTree Index Section: Flags: 0x0000 () Blocks: Previous (6109) Next (6305) Level (1) CycleId (0) 1ff0: dd170000 a1180000 01000000 00000000 ................ *** End of Requested Range Encountered. Last Block Read: 6246 *** Notice how item 2 has size 8, but regular entries have size 24. I know this is related to the high key of this page, but I can't quite figure out why the short entry is 2 not 1. Is item 2 just assumed to be greater than the previous' page high key? Page's 6109 high key is: Item 1 -- Length: 24 Offset: 8152 (0x1fd8) Flags: NORMAL Block Id: 6101 linp Index: 1 Size: 24 Has Nulls: 32768 Has Varwidths: 0 1fd8: 0000d517 01001880 01000000 00000000 ................ 1fe8: 8004f17d 6f230100 ...}o#.. Note that the data values are integer timestamp without time zone in little endian byte order. (The "Has Nulls" bit is somewhat bogus -- it displays 32768 when the 0x8000 bit is on, which is rather surprising. I'd expect it to display 1). -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
