postgrespro.git / summary / log / commit / refs

commit    ea4e1c0e8f583f99c8caab5bcdfbbbaaed0685c0
Author:   Tomas Vondra <tomas.vondra@postgresql.org>
Date:     Sat Mar 30 17:34:59 2019 +0000

    Additional fixes of memory alignment in pg_mcv_list code
    
    Commit d85e0f366a tried to fix memory alignment issues in serialization
    and deserialization of pg_mcv_list values, but it was a few bricks shy.
    The arrays of uint16 indexes in serialized items was not aligned, and
    the both the values and isnull flags were using the same pointer.
    
    Per investigation by Tom Lane on gaur.


 src/backend/statistics/mcv.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c
index e90a03fdf7..c5288b42d6 100644
--- a/src/backend/statistics/mcv.c
+++ b/src/backend/statistics/mcv.c
@@ -51,7 +51,7 @@
  *	 ndim * (sizeof(uint16) + sizeof(bool)) + 2 * sizeof(double)
  */
 #define ITEM_SIZE(ndims)	\
-	((ndims) * (sizeof(uint16) + sizeof(bool)) + 2 * sizeof(double))
+	MAXALIGN((ndims) * (sizeof(uint16) + sizeof(bool)) + 2 * sizeof(double))
 
 /*
  * Macros for convenient access to parts of a serialized MCV item.
@@ -929,8 +929,8 @@ statext_mcv_deserialize(bytea *data)
 	mcvlen = MAXALIGN(offsetof(MCVList, items) + (sizeof(MCVItem) * nitems));
 
 	/* arrays of values and isnull flags for all MCV items */
-	mcvlen += MAXALIGN(sizeof(Datum) * ndims * nitems);
-	mcvlen += MAXALIGN(sizeof(bool) * ndims * nitems);
+	mcvlen += nitems * MAXALIGN(sizeof(Datum) * ndims);
+	mcvlen += nitems * MAXALIGN(sizeof(bool) * ndims);
 
 	/* we don't quite need to align this, but it makes some assers easier */
 	mcvlen += MAXALIGN(datalen);
@@ -942,9 +942,9 @@ statext_mcv_deserialize(bytea *data)
 	valuesptr = (char *) mcvlist
 		+ MAXALIGN(offsetof(MCVList, items) + (sizeof(MCVItem) * nitems));
 
-	isnullptr = valuesptr + (MAXALIGN(sizeof(Datum) * ndims * nitems));
+	isnullptr = valuesptr + (nitems * MAXALIGN(sizeof(Datum) * ndims));
 
-	dataptr = isnullptr + (MAXALIGN(sizeof(bool) * ndims * nitems));
+	dataptr = isnullptr + (nitems * MAXALIGN(sizeof(bool) * ndims));
 
 	/*
 	 * Build mapping (index => value) for translating the serialized data into
@@ -1043,10 +1043,11 @@ statext_mcv_deserialize(bytea *data)
 		MCVItem    *item = &mcvlist->items[i];
 
 		item->values = (Datum *) valuesptr;
-		valuesptr += (sizeof(Datum) * ndims);
+		valuesptr += MAXALIGN(sizeof(Datum) * ndims);
+
+		item->isnull = (bool *) isnullptr;
+		isnullptr += MAXALIGN(sizeof(bool) * ndims);
 
-		item->isnull = (bool *) valuesptr;
-		valuesptr += (sizeof(bool) * ndims);
 
 		/* just point to the right place */
 		indexes = ITEM_INDEXES(ptr);


[parent: 7ad6498fd5a6]