Re: Conflict handling for COPY FROM

First of all, there is definitely a problem with grammar. In docs ERROR
is defined as option and

COPY test FROM '/path/to/copy-test-simple.csv' ERROR -1;

works just fine, but if modern 'WITH (...)' syntax is used:

COPY test FROM '/path/to/copy-test-simple.csv' WITH (ERROR -1);
ERROR:  option "error" not recognized

while 'WITH (error_limit -1)' it works again.

It happens, since COPY supports modern and very-very old syntax:

* In the preferred syntax the options are comma-separated
* and use generic identifiers instead of keywords.  The pre-9.0
* syntax had a hard-wired, space-separated set of options.

So I see several options here:

1) Everything is left as is, but then docs should be updated and
reflect, that error_limit is required for modern syntax.

2) However, why do we have to support old syntax here? I guess it exists
for backward compatibility only, but this is a completely new feature.
So maybe just 'WITH (error_limit 42)' will be enough?

3) You also may simply change internal option name from 'error_limit' to
'error' or SQL keyword from 'ERROR' tot 'ERROR_LIMIT'.

I would prefer the second option.

Next, you use DestRemoteSimple for returning conflicting tuples back:

+        dest = CreateDestReceiver(DestRemoteSimple);
+        dest->rStartup(dest, (int) CMD_SELECT, tupDesc);

However, printsimple supports very limited subset of built-in types, so

CREATE TABLE large_test (id integer primary key, num1 bigint, num2
double precision);
COPY large_test FROM '/path/to/copy-test.tsv';
COPY large_test FROM '/path/to/copy-test.tsv' ERROR 3;

fails with following error 'ERROR:  unsupported type OID: 701', which
seems to be very confusing from the end user perspective. I've tried to
switch to DestRemote, but couldn't figure it out quickly.

Finally, I simply cannot get into this validation:

+        else if (strcmp(defel->defname, "error_limit") == 0)
+        {
+            if (cstate->ignore_error)
+                ereport(ERROR,
+                        (errcode(ERRCODE_SYNTAX_ERROR),
+                         errmsg("conflicting or redundant options"),
+                         parser_errposition(pstate, defel->location)));
+            cstate->error_limit = defGetInt64(defel);
+            cstate->ignore_error = true;
+            if (cstate->error_limit == -1)
+                cstate->ignore_all_error = true;
+        }

If cstate->ignore_error is defined, then we have already processed
options list, since this is the only one place, where it's set. So we
should never get into this ereport, doesn't it?