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During table rewrites (VACUUM FULL and CLUSTER), the main heap is logged
using XLOG / FPI records, and thus (correctly) ignored in decoding.
But the associated TOAST table is WAL-logged as plain INSERT records,
and so was logically decoded and passed to reorder buffer.
That has severe consequences with TOAST tables of non-trivial size.
Firstly, reorder buffer has to keep all those changes, possibly spilling
them to a file, incurring I/O costs and disk space.
Secondly, ReoderBufferCommit() was stashing all those TOAST chunks into
a hash table, which got discarded only after processing the row from the
main heap. But as the main heap is not decoded for rewrites, this never
happened, so all the TOAST data accumulated in memory, resulting either
in excessive memory consumption or OOM.
The fix is simple, as commit
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backend | ||
bin | ||
common | ||
fe_utils | ||
include | ||
interfaces | ||
makefiles | ||
pl | ||
port | ||
template | ||
test | ||
timezone | ||
tools | ||
tutorial | ||
.gitignore | ||
DEVELOPERS | ||
Makefile | ||
Makefile.global.in | ||
Makefile.shlib | ||
nls-global.mk |