Explicit doc for the meaning of intersection_priority

src/postings/block_segment_postings.rs

@@ -97,8 +97,8 @@ impl BlockSegmentPostingsNotLoaded {
     /// Seek into the block segment postings directly, possibly avoiding loading its first block.
     pub fn seek_and_load(self, seek_doc: DocId) -> (BlockSegmentPostings, usize) {
         let BlockSegmentPostingsNotLoaded(mut block_segment_postings) = self;
-        block_segment_postings.load_block();
         let inner_pos = if seek_doc == 0 {
+            block_segment_postings.load_block();
             0
         } else {
             block_segment_postings.seek(seek_doc)

src/query/weight.rs

@@ -146,6 +146,10 @@ pub trait Weight: Send + Sync + 'static {
 
     /// Returns a priority number used to sort weights when running an
     /// intersection.
+    ///
+    /// Tweaking this value only impacts performance.
+    /// A higher priority means that the `.scorer()` will be more likely to be evaluated
+    /// after the sibling weights, and be passed a higher `seek_doc` value as a result.
     fn intersection_priority(&self) -> u32 {
         20u32
     }