temp table oddness?

I found weird behavior with temp tables.

test=> create table u1(i int);
CREATE
test=> insert into u1 values(1);
INSERT 3408201 1
test=> insert into u1 values(1);
INSERT 3408202 1
test=> create temp table u1(i int primary key);
NOTICE: CREATE TABLE/PRIMARY KEY will create implicit index 'u1_pkey' for table 'u1'
NOTICE: trying to delete a reldesc that does not exist.
NOTICE: trying to delete a reldesc that does not exist.
CREATE

Are these notices normal?

Next I exited the session and start psql again.

test=>
EOF
[t-ishii(at)ext16 Chapter3]$ !!
psql test
Welcome to the POSTGRESQL interactive sql monitor:
Please read the file COPYRIGHT for copyright terms of POSTGRESQL
[PostgreSQL 6.5.1 on powerpc-unknown-linux-gnu, compiled by gcc egcs-2.90.25 980302 (egcs-1.0.2 prerelease)]

type \? for help on slash commands
type \q to quit
type \g or terminate with semicolon to execute query
You are currently connected to the database: test

test=> create temp table u1(i int primary key);
NOTICE: CREATE TABLE/PRIMARY KEY will create implicit index 'u1_pkey' for table 'u1'
ERROR: Cannot create unique index. Table contains non-unique values

What's this? I thought temp tables completely mask persistent tables.
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Tatsuo Ishii