The following bug has been logged online:

Bug reference: 1936
Logged by: Alon Goldshuv
Email address: agoldshuv (AT) greenplum (DOT) com
PostgreSQL version: 8 (Current Dev)
Operating system: any
Description: Read-only transactions ignored in COPY
Details:

In the folllowing check (copy.coCopy() ), i *think* that the check for the
is_from flag is mistakenly negated. is_from means -> from file to database,
therefore we should check for <XactReadOnly && is_from>, and not
<XactReadOnly && !is_from>

/* check read-only transaction */
if (XactReadOnly && !is_from &&
!isTempNamespace(RelationGetNamespace(cstate->rel)))
ereport(ERROR,
(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
errmsg("transaction is read-only")));

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