Just encountered this error on an 8.1.2 cluster: LOG: statement: PREPARE dbdpg_5 AS SELECT * FROM foo WHERE visitnum = $1 and (scheduledtime >= $2 OR scheduledtime IS NULL) AND (scheduledtime < $3 OR scheduledtime IS NULL) UNION SELECT * FROM bar WHERE visitnum = $4 ORDER BY scheduledtime LOG: statement: <BIND> LOG: statement: EXECUTE <unnamed> [PREPARE: SELECT * FROM foo WHERE visitnum = $1 and (scheduledtime >= $2 OR scheduledtime IS NULL) AND (scheduledtime < $3 OR scheduledtime IS NULL) UNION SELECT * FROM bar WHERE visitnum = $4 ORDER BY scheduledtime] ERROR: direct correlated subquery unsupported as initplan A run of 'analyze' seems to have made the error go away. Here's our version: PostgreSQL 8.1.2 on ia64-unknown-linux-gnu, compiled by GCC gcc (GCC) 3.4.3 20050227 (Red Hat 3.4.3-22.1) Any clues? Thanks, Ed