On Tue, Feb 14, 2017 at 3:19 PM, Seki, Eiji <seki.e...@jp.fujitsu.com> wrote:
> This change will be useful for features that only reads rows that are visible 
> by all transactions and could not wait specific processes (VACUUM, ANALYZE, 
> etc...) for performance. Our company (Fujitsu) is developing such an 
> extension. In our benchmark, we found that waiting an ANALYZE process created 
> by autovacuum daemon often has a significant impact to the performance 
> although the waited process do only reading as to the table. So I hope to 
> ignore it using GetOldestXminExtend as below. The second argument represents 
> flags to ignore.
>   GetOldestXminExtended(rel, PROC_IN_VACUUM | PROC_IN_LOGICAL_DECODING | 
> Note: We can ignore VACUUM processes or VACUUM with ANALYZE processes using 
> the second option of GetOldesXmin, "ignoreVacuum". However, we cannot ignore 
> only ANALYZE processes because the "ignoreVacuum" = true is same to the 
> following.

 GetOldestXmin(Relation rel, bool ignoreVacuum)
+   uint8 ignoreFlags = PROC_IN_LOGICAL_DECODING;
+   if (ignoreVacuum)
+       ignoreFlags |= PROC_IN_VACUUM;
+   return GetOldestXminExtended(rel, ignoreFlags);

It seems to me that it would be far less confusing to just replace the
boolean argument of GetOldestXmin by a uint8 and get those flags
declared in procarray.h, no? There are a couple of code path calling
GetOldestXmin() that do not include proc.h, so it would be better to
not add any extra header dependencies in those files.

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