[HACKERS] LEFT JOIN used in psql describe.c

[Bruce Momjian]

Does anyone know why so many LEFT JOINs are used in psql/describe.c to
join to the pg_namespace table, like here:

   printfPQExpBuffer(&buf,
      "SELECT c.oid,\n"
      "  n.nspname,\n"
      "  c.relname\n"
      "FROM pg_catalog.pg_class c\n"
      "     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace\n");

    processNamePattern(&buf, pattern, false, false,
       "n.nspname", "c.relname", NULL,
       "pg_catalog.pg_table_is_visible(c.oid)");

I thought a pg_class row always pointed to a valid pg_namespace row because
of our dependency restrictions.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
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