Re: [HACKERS] [PATCH] pageinspect function to decode infomasks - Mailing list pgsql-hackers

Dear Craig Ringer

 

Frist, thank you for implementing the necessary function.

 

but, i have some question.

 

question 1) vacuum freeze hint bits

If run a vacuum freeze, bits in the infomask will be 0x0300.

in this case, if output the value of informsk in the run to you modified,

HEAP_XMIN_COMMITTED(0x0100), HEAP_XMIN_INVALID(0x0200), HEAP_XMIN_FROZEN(0x0300)

all outputs to hint bits.

 

is it normal to output values?

 

if look at htup_details.h code,

 

#define HeapTupleHeaderXminInvalid(tup) \

( \

              ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \

                            HEAP_XMIN_INVALID \

)

#define HeapTupleHeaderSetXminCommitted(tup) \

( \

              AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \

              ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \

)

 

HEAP_XMIN_INVALID and HEAP_XMIN_COMMITTED can not be write simultaneously.

question 2) xmax lock hint bits

similar to the vacuum freezeze question..

Assume that the infomask has a bit of 0x0050

 

In this case, if run on the code that you modified,

HEAP_XMAX_KEYSHR_LOCK(0x0010), HEAP_XMAX_EXCL_LOCK(0x0040), HEAP_XMAX_IS_LOCKED_ONLY

three hint bits are the output.

 

if look at htup_details.h code,

 

#define HEAP_XMAX_IS_SHR_LOCKED(infomask) \

              (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK)

#define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \

              (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK)

#define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \

              (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK)

 

It is divided into to hint bits.

so I think this part needs to fix.