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Additional fixes of memory alignment in pg_mcv_list code

Commitd85e0f3 tried to fix memory alignment issues in serializationand deserialization of pg_mcv_list values, but it was a few bricks shy.The arrays of uint16 indexes in serialized items was not aligned, andthe both the values and isnull flags were using the same pointer.Per investigation by Tom Lane on gaur.

1 parent7ad6498 commitea4e1c0Copy full SHA for ea4e1c0

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lines changed

src/backend/statistics
- mcv.c

1 file changed

-8

lines changed

`‎src/backend/statistics/mcv.c`

Lines changed: 9 additions & 8 deletions

Original file line number	Diff line number	Diff line change
`@@ -51,7 +51,7 @@`
`51`	`51`	`* ndim * (sizeof(uint16) + sizeof(bool)) + 2 * sizeof(double)`
`52`	`52`	`*/`
`53`	`53`	`#defineITEM_SIZE(ndims)\`
`54`		`-((ndims) * (sizeof(uint16) + sizeof(bool)) + 2 * sizeof(double))`
	`54`	`+MAXALIGN((ndims) * (sizeof(uint16) + sizeof(bool)) + 2 * sizeof(double))`
`55`	`55`
`56`	`56`	`/*`
`57`	`57`	`* Macros for convenient access to parts of a serialized MCV item.`
`@@ -929,8 +929,8 @@ statext_mcv_deserialize(bytea *data)`
`929`	`929`	`mcvlen=MAXALIGN(offsetof(MCVList,items)+ (sizeof(MCVItem)*nitems));`
`930`	`930`
`931`	`931`	`/* arrays of values and isnull flags for all MCV items */`
`932`		`-mcvlen+=MAXALIGN(sizeof(Datum)ndimsnitems);`
`933`		`-mcvlen+=MAXALIGN(sizeof(bool)ndimsnitems);`
	`932`	`+mcvlen+=nitemsMAXALIGN(sizeof(Datum)ndims);`
	`933`	`+mcvlen+=nitemsMAXALIGN(sizeof(bool)ndims);`
`934`	`934`
`935`	`935`	`/* we don't quite need to align this, but it makes some assers easier */`
`936`	`936`	`mcvlen+=MAXALIGN(datalen);`
`@@ -942,9 +942,9 @@ statext_mcv_deserialize(bytea *data)`
`942`	`942`	`valuesptr= (char*)mcvlist`
`943`	`943`	`+MAXALIGN(offsetof(MCVList,items)+ (sizeof(MCVItem)*nitems));`
`944`	`944`
`945`		`-isnullptr=valuesptr+ (MAXALIGN(sizeof(Datum)ndimsnitems));`
	`945`	`+isnullptr=valuesptr+ (nitemsMAXALIGN(sizeof(Datum)ndims));`
`946`	`946`
`947`		`-dataptr=isnullptr+ (MAXALIGN(sizeof(bool)ndimsnitems));`
	`947`	`+dataptr=isnullptr+ (nitemsMAXALIGN(sizeof(bool)ndims));`
`948`	`948`
`949`	`949`	`/*`
`950`	`950`	`* Build mapping (index => value) for translating the serialized data into`
`@@ -1043,10 +1043,11 @@ statext_mcv_deserialize(bytea *data)`
`1043`	`1043`	`MCVItem*item=&mcvlist->items[i];`
`1044`	`1044`
`1045`	`1045`	`item->values= (Datum*)valuesptr;`
`1046`		`-valuesptr+= (sizeof(Datum)*ndims);`
	`1046`	`+valuesptr+=MAXALIGN(sizeof(Datum)*ndims);`
	`1047`	`+`
	`1048`	`+item->isnull= (bool*)isnullptr;`
	`1049`	`+isnullptr+=MAXALIGN(sizeof(bool)*ndims);`
`1047`	`1050`
`1048`		`-item->isnull= (bool*)valuesptr;`
`1049`		`-valuesptr+= (sizeof(bool)*ndims);`
`1050`	`1051`
`1051`	`1052`	`/* just point to the right place */`
`1052`	`1053`	`indexes=ITEM_INDEXES(ptr);`

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Commitea4e1c0

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`‎src/backend/statistics/mcv.c`

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