Here are my initial review comments for the first patch v20240625-0001.
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General
1. Missing docs?
Section 9.17. "Sequence Manipulation Functions" [1] describes some
functions. Shouldn't your new function be documented here also?
~~~
2. Missing tests?
Shouldn't there be some test code that at least executes your new
pg_sequence_state function to verify that sane values are returned?
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Commit Message
3.
This patch introduces new functionalities to PostgreSQL:
- pg_sequence_state allows retrieval of sequence values using LSN.
- SetSequence enables updating sequences with user-specified values.
~
3a.
I didn't understand why this says "using LSN" because IIUC 'lsn' is an
output parameter of that function. Don't you mean "... retrieval of
sequence values including LSN"?
~
3b.
Does "user-specified" make sense? Is this going to be exposed to a
user? How about just "specified"?
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src/backend/commands/sequence.c
4. SetSequence:
+void
+SetSequence(Oid seq_relid, int64 value)
Would 'new_last_value' be a better parameter name here?
~~~
5.
This new function logic looks pretty similar to the do_setval()
function. Can you explain (maybe in the function comment) some info
about how and why it differs from that other function?
~~~
6.
I saw that RelationNeedsWAL() is called 2 times. It may make no sense,
but is it possible to assign that to a variable 1st time so you don't
need to call it 2nd time within the critical section?
~~~
NITPICK - remove junk (') char in comment
NITPICK - missing periods (.) in multi-sentence comment
~~~
7.
-read_seq_tuple(Relation rel, Buffer *buf, HeapTuple seqdatatuple)
+read_seq_tuple(Relation rel, Buffer *buf, HeapTuple seqdatatuple,
+ XLogRecPtr *lsn)
7a.
The existing parameters were described in the function comment. So,
the new 'lsn' parameter should be described here also.
~
7b.
Maybe the new parameter name should be 'lsn_res' or 'lsn_out' or
similar to emphasise that this is a returned value.
~~
NITPICK - tweaked comment. YMMV.
~~~
8. pg_sequence_state:
Should you give descriptions of the output parameters in the function
header comment? Otherwise, where are they described so called knows
what they mean?
~~~
NITPICK - /relid/seq_relid/
NITPICK - declare the variables in the same order as the output parameters
NITPICK - An alternative to the memset for nulls is just to use static
initialisation
"bool nulls[4] = {false, false, false, false};"
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+extern void SetSequence(Oid seq_relid, int64 value);
9.
Would 'SetSequenceLastValue' be a better name for what this function is doing?
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99.
See also my attached diff which is a top-up patch implementing those
nitpicks mentioned above. Please apply any of these that you agree
with.
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[1] https://www.postgresql.org/docs/devel/functions-sequence.html
Kind Regards,
Peter Smith.
Fujitsu Australia