Thread
Commits
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Report expected contrecord length on mismatch
- f43e295f68c3 14.0 landed
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report expected contrecord size
Alvaro Herrera <alvherre@2ndquadrant.com> — 2020-09-03T21:21:52Z
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. -- Álvaro Herrera http://www.flickr.com/photos/alvherre/
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Re: report expected contrecord size
Tom Lane <tgl@sss.pgh.pa.us> — 2020-09-03T21:31:31Z
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
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Re: report expected contrecord size
Alvaro Herrera <alvherre@2ndquadrant.com> — 2020-09-03T22:00:34Z
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). -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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Re: report expected contrecord size
Tom Lane <tgl@sss.pgh.pa.us> — 2020-09-03T22:17:30Z
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
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Re: report expected contrecord size
Alvaro Herrera <alvherre@2ndquadrant.com> — 2020-09-03T22:33:08Z
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.) -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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Re: report expected contrecord size
Tom Lane <tgl@sss.pgh.pa.us> — 2020-09-03T22:42:02Z
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
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Re: report expected contrecord size
Alvaro Herrera <alvherre@2ndquadrant.com> — 2020-09-04T19:00:26Z
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. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services