fix unsafe rows.Close() race#726
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erykwalder wants to merge 1 commit intolib:masterfrom
erykwalder:scratch-race
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fix unsafe rows.Close() race#726erykwalder wants to merge 1 commit intolib:masterfrom erykwalder:scratch-race
erykwalder wants to merge 1 commit intolib:masterfrom
erykwalder:scratch-race
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According to https://godoc.org/database/sql/driver#Rows, the Close operation should not affect the values returned by Scan. In normal flow, this is not an issue, but if Rows is closed by a cancelled context or another routine, it can be. This changes the scratch to be a slice, and changes its memory location when rows are closed before they are done, so that any scanning will not be affected.
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I can't really simulate a case where this causes problems for us. I think the current logic should be fine? I see a number of changes/fixes in database/sql related to this as well over the last few years so it's possible this used to be a problem but is no longer. Since this is a few years old I'll just go ahead and close it, but feel free to come back with more details if I'm mistaken we can re-open. |
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According to https://godoc.org/database/sql/driver#Rows, the Close
operation should not affect the values returned by Next. In normal flow,
this is not an issue, but if Rows is closed by a cancelled context or
another routine, it can be.
This changes the scratch to be a slice, and changes its memory location
when rows are closed before they are done, so that any scanning will not
be affected.
In an attempt to prevent allocations every time the rows are closed,
this only creates a new scratch when rows are closed before they
are done.