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Rewrite phase is also supposed to "flatten subqueries/views" (cf. "Extensible/rule based query rewrite optimization in Starburst"; SIGMOD 92) and can be fairly

Rewrite phase is also supposed to "flatten subqueries/views" (cf. "Extensible/rule based query rewrite optimization in Starburst"; SIGMOD 92) and can be fairly complex. PostgreSQL doesn't do it to the same extent as DB2, but there is certainly some complex logic involved there.

anarazel 10y ago
That paper's definition of rewriting isn't the same as postgres' (they even say that: "The work presented here should not be confused with the query rewrite facility of POSTGRES [SJGP90]."). Flattening subqueries and views happens during planning in postgres. Source: I'm a PostgreSQL Developer.