A line like SELECT name FROM users WHERE id = 1 arrives at the backend. As we saw in 1.1.1, the backend is a child process forked by the postmaster when the client connects, dedicated to that one client. What this process first holds in its hands is just a byte array. It does not yet know where the keywords end, where the identifiers begin, or where the integer constant lives. Turning that byte array into a tree structure is the front half of the second of the five stages, namely raw parsing. This section covers only that front half. The back half (parse analysis), which consults the catalog to attach meaning, belongs to 1.2.2. (The catalog, in case you need a refresher, is the set of internal tables PostgreSQL maintains to describe itself: which tables have which columns, which functions take which argument types, and so on, all stored as rows in these tables.) The output of raw parsing is a single RawStmt node per SQL string (or a List, if multiple statements are joined with ; ).…