Enum DeferredDictionaryPage 

enum DeferredDictionaryPage {
    Header {
        data_start: u64,
        header: Box<PageHeader>,
    },
    Location(PageLocation),
}

Location of a dictionary page skipped without decoding.

           skip, and the reader can defer         first data page that
           (record location, zero decompress)     needs the dictionary
  NotSeen ─────────────────────────────▶ Deferred ─────────────────────▶ Decoded
     │                                                                      ▲
     ├── read hits the dictionary page (eager path, unchanged) ─────────────┤
     │                                                                      │
     └── skip, but the reader cannot defer ─────────────────────────────────┘
         (`supports_deferred_dictionary()` is false: read it eagerly,
          because a skipped page this reader cannot hand back is lost)

A chunk skipped end to end stays Deferred: its dictionary is never decompressed, which is the point. Skipping values needs only the RLE index cursor, and skipping whole pages needs nothing at all, so the only consumer of dictionary contents is value decoding. Random re-read is what makes the deferral safe: ChunkReader hands out readers at any offset, and the async path’s in-memory column chunk already holds the page’s bytes.

Variants

Header

Values state: the header was already parsed on the skip path, only the page body was left untouched.

Fields

data_start: u64

header: Box<PageHeader>

Location(PageLocation)

Pages state: the offset index records the page location; header and body are both still unread.