On Wed, Jun 22, 2016 at 4:11 AM, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote: >> In an outer join we have to differentiate between a row being null (because >> there was no joining row on nullable side) and a non-null row with all >> column values being null. If we cast the whole-row expression to a text >> e.g. r.*::text and test the resultant value for nullness, it gives us what >> we want. A null row casted to text is null and a row with all null values >> casted to text is not null. > > You are right. There may be non-null rows with all columns null which are > handled wrongly (as Rushabh reports) and the hack I proposed is not right > for. Especially if from non-nullable side as in the reported case, NULL > test for such a whole-row-var would produce the wrong result. Casting to > text as your patch does produces the correct behavior.
I agree, but I think we'd better cast to pg_catalog.text instead, just to be safe. Committed that way.
postgres_fdw resets the search path to pg_catalog while opening connection to the server. The reason behind this is explained in deparse.c
* We assume that the remote session's search_path is exactly "pg_catalog", * and thus we need schema-qualify all and only names outside pg_catalog.
So, we should not be schema-qualifying types while casting. From deparse.c /* * Convert type OID + typmod info into a type name we can ship to the remote * server. Someplace else had better have verified that this type name is * expected to be known on the remote end. * * This is almost just format_type_with_typemod(), except that if left to its * own devices, that function will make schema-qualification decisions based * on the local search_path, which is wrong. We must schema-qualify all * type names that are not in pg_catalog. We assume here that built-in types * are all in pg_catalog and need not be qualified; otherwise, qualify. */ static char * deparse_type_name(Oid type_oid, int32 typemod) { if (is_builtin(type_oid)) return format_type_with_typemod(type_oid, typemod); else return format_type_with_typemod_qualified(type_oid, typemod); }
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Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company