Invert the word docid positions key order

src/heed_codec/beu32_str_codec.rs

@@ -2,26 +2,26 @@ use std::borrow::Cow;
 use std::convert::TryInto;
 use std::str;
 
-pub struct StrBEU32Codec;
+pub struct BEU32StrCodec;
 
-impl<'a> heed::BytesDecode<'a> for StrBEU32Codec {
-    type DItem = (&'a str, u32);
+impl<'a> heed::BytesDecode<'a> for BEU32StrCodec {
+    type DItem = (u32, &'a str);
 
     fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
-        let (str_bytes, n_bytes) = bytes.split_at(bytes.len() - 4);
-        let s = str::from_utf8(str_bytes).ok()?;
+        let (n_bytes, str_bytes) = bytes.split_at(4);
         let n = n_bytes.try_into().map(u32::from_be_bytes).ok()?;
-        Some((s, n))
+        let s = str::from_utf8(str_bytes).ok()?;
+        Some((n, s))
     }
 }
 
-impl<'a> heed::BytesEncode<'a> for StrBEU32Codec {
-    type EItem = (&'a str, u32);
+impl<'a> heed::BytesEncode<'a> for BEU32StrCodec {
+    type EItem = (u32, &'a str);
 
-    fn bytes_encode((s, n): &Self::EItem) -> Option<Cow<[u8]>> {
+    fn bytes_encode((n, s): &Self::EItem) -> Option<Cow<[u8]>> {
         let mut bytes = Vec::with_capacity(s.len() + 4);
-        bytes.extend_from_slice(s.as_bytes());
         bytes.extend_from_slice(&n.to_be_bytes());
+        bytes.extend_from_slice(s.as_bytes());
         Some(Cow::Owned(bytes))
     }
 }

src/heed_codec/mod.rs

@@ -1,7 +1,7 @@
 mod csv_string_record_codec;
 mod roaring_bitmap_codec;
-mod str_beu32_codec;
+mod beu32_str_codec;
 
 pub use self::csv_string_record_codec::CsvStringRecordCodec;
 pub use self::roaring_bitmap_codec::RoaringBitmapCodec;
-pub use self::str_beu32_codec::StrBEU32Codec;
+pub use self::beu32_str_codec::BEU32StrCodec;