Re: Xmax precedes relation freeze threshold errors

On 2022-Jun-16, Sergey Aleynikov wrote:

> (verify_heapam before)
> blkno | offnum | attnum | msg
> -------+--------+--------+-----------------------------------------------------------------
> 20365 | 8 | | xmax 1965224948 precedes relation freeze threshold 1:1914858032
> 20365 | 12 | | xmin 1965224948 precedes relation freeze threshold 1:1914858032
> (2 rows)

Hmm, well, these errors make no sense, because 1965224948 is definitely
not earlier than the stated threshold of 1914858032. There might be a
bug in the amcheck conversion of the epochless XID value to FullXid, or
in the comparison functions.

For the record, the values for this page are below. For (20365,8) the
infomask is 0x2102 which is HEAP_UPDATED | HEAP_XMIN_COMMITTED; there's
no bit for Xmax. The next one in the chain is the other
complained-about tuple, (20365,12) which has a matching Xmin (no
surprise there) and the infomask is 0x2092 which is HEAP_UPDATED |
HEAP_XMAX_LOCK_ONLY | HEAP_XMAX_KEYSHR_LOCK. So this is a tuple that
was updated and then the new version was used by SELECT FOR KEY SHARE.
Nothing strange here.

lp | lp_off | lp_flags | lp_len | t_xmin | t_xmax | t_field3 | t_ctid | t_infomask2 | t_infomask | t_hoff | t_bits | t_oid | t_data
----+--------+----------+--------+------------+------------+----------+------------+-------------+------------+--------+--------+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 | 25 | 2 | 0 | | | | | | | | | |
2 | 4504 | 1 | 204 | 1965224930 | 1965224938 | 6 | (20365,8) | 57347 | 9474 | 24 | | | \016\301\177\005\000\000\000\000\300\271\261\265\215\204\002\000\220\002\000\000[[1,0,1655367415],[2,0,1655368111],[3,0,1655316514],[4,1,1345141307],[7,0,1655368111],[10,46,1655368114],[12,0,1655316561],[13,2,1602489365],[16,20,1655368127]]
3 | 8040 | 1 | 147 | 1852898199 | 0 | 38 | (20365,3) | 3 | 11010 | 24 | | | \205<\207\005\000\000\000\000\200\317f\023/\202\002\000\327[[1,0,1649925421],[2,3,1652762654],[4,1,1336885001],[7,0,1652762654],[10,49,1649925346],[16,0,1649925383]]
4 | 27 | 2 | 0 | | | | | | | | | |
5 | 7768 | 1 | 272 | 1964963817 | 1964963897 | 7 | (20365,5) | 40963 | 10690 | 24 | | | \035(\345\005\000\000\000\000\300\301\017\300\213\204\002\000\240\003\000\000[[1,0,1655356016],[2,0,1655355988],[3,0,1655359711],[4,1,1318680670],[6,1,1580191566],[7,0,1655355987],[8,4,1580191566],[9,3,1580191566],[10,39,1655358356],[12,1,1580280953],[13,3,1580191566],[14,0,1580191566],[16,0,1594455141]]
6 | 7488 | 1 | 273 | 1904288297 | 0 | 7 | (20365,6) | 32771 | 11010 | 24 | | | H\032\311\005\000\000\000\000\3007\252\326`\203\002\000\244\003\000\000[[1,1,1638359432],[2,8,1654075863],[3,0,1654075895],[4,1,1411368668],[6,0,1643527342],[7,0,1654075863],[8,4,1586241825],[9,3,1586241825],[10,48,1653909745],[12,1,1586241825],[13,3,1586241825],[14,0,1586241825],[16,30,1586241825]]
7 | 32 | 2 | 0 | | | | | | | | | |
8 | 4296 | 1 | 204 | 1965224938 | 1965224948 | 6 | (20365,12) | 57347 | 8450 | 24 | | | \016\301\177\005\000\000\000\000\300\271\261\265\215\204\002\000\220\002\000\000[[1,0,1655367415],[2,0,1655368111],[3,0,1655316514],[4,1,1345141307],[7,0,1655368111],[10,46,1655368114],[12,0,1655316561],[13,2,1602489365],[16,19,1655368127]]
9 | 6 | 2 | 0 | | | | | | | | | |
10 | 29 | 2 | 0 | | | | | | | | | |
11 | 7208 | 1 | 273 | 1965056934 | 1965056934 | 7 | (20365,11) | 32771 | 10642 | 24 | | | \377\232\310\005\000\000\000\000\200\271\334q\214\204\002\000\244\003\000\000[[1,0,1655361162],[2,5,1655361996],[3,0,1655362694],[4,1,1358874131],[6,0,1655055632],[7,0,1655361158],[8,4,1580366031],[9,3,1639915217],[10,46,1655361947],[12,1,1653134366],[13,3,1580366031],[14,0,1580366031],[16,30,1580366031]]
12 | 4088 | 1 | 204 | 1965224948 | 1965224948 | 6 | (20365,12) | 32771 | 8338 | 24 | | | \016\301\177\005\000\000\000\000\000\374\300\265\215\204\002\000\220\002\000\000[[1,0,1655367415],[2,0,1655368111],[3,0,1655316514],[4,1,1345141307],[7,0,1655368111],[10,46,1655368114],[12,0,1655316561],[13,2,1602489365],[16,18,1655368128]]
13 | 7160 | 1 | 43 | 1957335917 | 1964638027 | 1 | (20365,13) | 8195 | 2498 | 24 | | | \310jo\007\000\000\000\000\200\027k\264b\204\002\000\007[]
14 | 16 | 2 | 0 | | | | | | | | | |
15 | 0 | 0 | 0 | | | | | | | | | |
16 | 6880 | 1 | 273 | 1965223751 | 1965223751 | 8 | (20365,16) | 32771 | 10642 | 24 | | | \347\243\236\005\000\000\000\000\300h\214\263\215\204\002\000\244\003\000\000[[1,0,1655240440],[2,9,1655368091],[3,0,1654972875],[4,1,1397413995],[6,0,1654175940],[7,0,1655368091],[8,4,1582557307],[9,3,1582557307],[10,47,1654197675],[12,1,1629279335],[13,3,1587923475],[14,0,1582557307],[16,30,1648131697]]
17 | 0 | 0 | 0 | | | | | | | | | |
18 | 0 | 0 | 0 | | | | | | | | | |
19 | 0 | 0 | 0 | | | | | | | | | |
20 | 0 | 0 | 0 | | | | | | | | | |
21 | 0 | 0 | 0 | | | | | | | | | |
22 | 0 | 0 | 0 | | | | | | | | | |
23 | 0 | 0 | 0 | | | | | | | | | |
24 | 0 | 0 | 0 | | | | | | | | | |
25 | 6640 | 1 | 238 | 1490075747 | 0 | 5 | (20365,25) | 32771 | 11010 | 24 | | | \373\021J\007\000\000\000\000\300\207\236\331|z\002\000\030\003\000\000[[1,0,1644300599],[2,10,1643357339],[3,4,1643109769],[6,0,1643357339],[7,0,1643365735],[8,4,1643357339],[9,3,1643357339],[12,0,1643360113],[13,3,1643108769],[14,0,1643357339],[16,30,1643357339]]
26 | 0 | 0 | 0 | | | | | | | | | |
27 | 6360 | 1 | 273 | 1962697004 | 1962697004 | 7 | (20365,27) | 32771 | 10642 | 24 | | | \3342\251\005\000\000\000\000\200\020\230\276x\204\002\000\244\003\000\000[[1,1,1655183659],[2,9,1655278082],[3,4,1655217231],[4,1,1646965839],[6,0,1655275445],[7,0,1655278082],[8,4,1636371136],[9,3,1636371136],[10,46,1655182361],[12,1,1648303165],[13,3,1636371136],[14,0,1636371136],[16,30,1636371136]]
28 | 0 | 0 | 0 | | | | | | | | | |
29 | 6080 | 1 | 273 | 1964885708 | 1964885708 | 9 | (20365,29) | 32771 | 10642 | 24 | | | y\031\300\006\000\000\000\000\300=&.\213\204\002\000\244\003\000\000[[1,0,1655356874],[2,0,1655356785],[3,3,1655356828],[4,0,1607932548],[6,0,1593701110],[7,0,1655356785],[8,4,1589636764],[9,3,1589636764],[10,45,1655357263],[12,0,1655223006],[13,2,1633191479],[14,0,1589636764],[16,22,1655285002]]
30 | 5 | 2 | 0 | | | | | | | | | |
31 | 6032 | 1 | 43 | 1529256935 | 0 | 1 | (20365,31) | 3 | 2818 | 24 | | | z\315N\007\000\000\000\000\000\207\037)0{\002\000\007[]
32 | 5752 | 1 | 273 | 1964761973 | 1964761973 | 7 | (20365,32) | 32771 | 10642 | 24 | | | \377\020\322\005\000\000\000\000\000d\303+\212\204\002\000\244\003\000\000[[1,1,1635340514],[2,8,1655352336],[3,0,1655352928],[4,1,1324578627],[6,0,1652362638],[7,0,1655352336],[8,4,1580283680],[9,3,1580283680],[10,49,1655321899],[12,1,1623273443],[13,3,1580283680],[14,0,1580283680],[16,30,1580283680]]
33 | 0 | 0 | 0 | | | | | | | | | |
34 | 0 | 0 | 0 | | | | | | | | | |
35 | 5472 | 1 | 273 | 1962530750 | 1962530750 | 9 | (20365,35) | 32771 | 10642 | 24 | | | "\273o\005\000\000\000\000\200\024\276\206w\204\002\000\244\003\000\000[[1,0,1655272251],[2,6,1655272847],[3,0,1655110969],[4,1,1364884674],[6,0,1649045620],[7,0,1655272847],[8,4,1621844466],[9,3,1621844466],[10,49,1655272850],[12,1,1635832362],[13,3,1621821962],[14,0,1621844466],[16,30,1621844466]]
36 | 5264 | 1 | 204 | 1965224703 | 1965224917 | 6 | (20365,38) | 57347 | 9474 | 24 | | | \016\301\177\005\000\000\000\000\300\2477\265\215\204\002\000\220\002\000\000[[1,0,1655367415],[2,0,1655368111],[3,0,1655316514],[4,1,1345141307],[7,0,1655368111],[10,46,1655368114],[12,0,1655316561],[13,2,1602489365],[16,23,1655368119]]
37 | 5128 | 1 | 129 | 1964847563 | 1964847563 | 7 | (20365,37) | 32771 | 10642 | 24 | | | \201A\250\005\000\000\000\000\300\215\253\345\212\204\002\000\263[[1,0,1655355920],[2,6,1655355999],[3,0,1655356047],[7,0,1655355997],[10,46,1655356007]]
38 | 4920 | 1 | 204 | 1965224917 | 1965224925 | 6 | (20365,39) | 57347 | 9474 | 24 | | | \016\301\177\005\000\000\000\000\200w\242\265\215\204\002\000\220\002\000\000[[1,0,1655367415],[2,0,1655368111],[3,0,1655316514],[4,1,1345141307],[7,0,1655368111],[10,46,1655368114],[12,0,1655316561],[13,2,1602489365],[16,22,1655368126]]
39 | 4712 | 1 | 204 | 1965224925 | 1965224930 | 6 | (20365,2) | 57347 | 9474 | 24 | | | \016\301\177\005\000\000\000\000\200w\242\265\215\204\002\000\220\002\000\000[[1,0,1655367415],[2,0,1655368111],[3,0,1655316514],[4,1,1345141307],[7,0,1655368111],[10,46,1655368114],[12,0,1655316561],[13,2,1602489365],[16,21,1655368126]]
40 | 0 | 0 | 0 | | | | | | | | | |
41 | 0 | 0 | 0 | | | | | | | | | |
42 | 0 | 0 | 0 | | | | | | | | | |
43 | 0 | 0 | 0 | | | | | | | | | |
44 | 0 | 0 | 0 | | | | | | | | | |
45 | 35 | 2 | 0 | | | | | | | | | |
46 | 0 | 0 | 0 | | | | | | | | | |
47 | 37 | 2 | 0 | | | | | | | | | |
48 | 11 | 2 | 0 | | | | | | | | | |
49 | 0 | 0 | 0 | | | | | | | | | |
50 | 0 | 0 | 0 | | | | | | | | | |
51 | 36 | 2 | 0 | | | | | | | | | |
(51 rows)

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Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"Always assume the user will do much worse than the stupidest thing
you can imagine." (Julien PUYDT)