report expected contrecord size
A pretty minor issue: when reporting that WAL appears invalid because
contrecord length doesn't match, we may as well print to the server log
the value that we're expecting. Patch attached.
--
�lvaro Herrera http://www.flickr.com/photos/alvherre/
Attachments:
report-contrecord.patchtext/x-diff; charset=us-asciiDownload+2-1
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
A pretty minor issue: when reporting that WAL appears invalid because
contrecord length doesn't match, we may as well print to the server log
the value that we're expecting. Patch attached.
ITYW
+ (long long) (total_len - gotlen),
just to be sure about what's getting casted to what. Otherwise +1.
regards, tom lane
On 2020-Sep-03, Tom Lane wrote:
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
A pretty minor issue: when reporting that WAL appears invalid because
contrecord length doesn't match, we may as well print to the server log
the value that we're expecting. Patch attached.ITYW
+ (long long) (total_len - gotlen),
just to be sure about what's getting casted to what.
Well, the intention there is to cast the first operand (which is uint32)
so that it turns into signed 64-bits; the subtraction then occurs in 64
bit arithmetic normally. If I let the subtraction occur in 32-bit width
unsigned, the result might overflow 32 bits. I'm thinking in
1 - UINT32_MAX or some such.
Maybe to make that more explicit, it should be
+ ((long long) total_len) - gotlen,
(If I understand the precedence correctly, it's the same thing I wrote).
--
�lvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
Well, the intention there is to cast the first operand (which is uint32)
so that it turns into signed 64-bits; the subtraction then occurs in 64
bit arithmetic normally. If I let the subtraction occur in 32-bit width
unsigned, the result might overflow 32 bits.
Uh ... is it really possible for gotlen to be more than total_len?
(I've not looked at the surrounding code here, but that seems weird.)
regards, tom lane
On 2020-Sep-03, Tom Lane wrote:
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
Well, the intention there is to cast the first operand (which is uint32)
so that it turns into signed 64-bits; the subtraction then occurs in 64
bit arithmetic normally. If I let the subtraction occur in 32-bit width
unsigned, the result might overflow 32 bits.Uh ... is it really possible for gotlen to be more than total_len?
(I've not looked at the surrounding code here, but that seems weird.)
Well, as I understand, total_len comes from one page, and gotlen comes
from the continuation record(s) in the next page(s) of WAL. So if
things are messed up, it could happen. (This *is* the code that
validates the record, so it can't make too many assumptions.)
--
�lvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
On 2020-Sep-03, Tom Lane wrote:
Uh ... is it really possible for gotlen to be more than total_len?
(I've not looked at the surrounding code here, but that seems weird.)
Well, as I understand, total_len comes from one page, and gotlen comes
from the continuation record(s) in the next page(s) of WAL. So if
things are messed up, it could happen. (This *is* the code that
validates the record, so it can't make too many assumptions.)
Got it. No further objections.
regards, tom lane
On 2020-Sep-03, Tom Lane wrote:
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
On 2020-Sep-03, Tom Lane wrote:
Uh ... is it really possible for gotlen to be more than total_len?
(I've not looked at the surrounding code here, but that seems weird.)Well, as I understand, total_len comes from one page, and gotlen comes
from the continuation record(s) in the next page(s) of WAL. So if
things are messed up, it could happen. (This *is* the code that
validates the record, so it can't make too many assumptions.)Got it. No further objections.
Many thanks for looking! Pushed now.
--
�lvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services