anoopj commented on code in PR #17198:
URL: https://github.com/apache/iceberg/pull/17198#discussion_r3582475951


##########
format/spec.md:
##########
@@ -700,6 +700,10 @@ The `sequence_number` field represents the data sequence 
number and must never c
 The `file_sequence_number` field represents the sequence number of the 
snapshot that added the file and must also remain unchanged upon assigning at 
commit. The file sequence number can't be used for pruning delete files as the 
data within the file may have an older data sequence number.
 The data and file sequence numbers are inherited only if the entry status is 1 
(added). If the entry status is 0 (existing) or 2 (deleted), the entry must 
include both sequence numbers explicitly.
 
+#### Content file uniqueness
+
+Within a snapshot, each live manifest entry must be uniquely defined by 
`file_path` across all manifest files. A snapshot with multiple live entries 
for the same `file_path` has undefined behavior. Writers are not required to 
validate uniqueness because doing so can be expensive at commit time.

Review Comment:
   How about stating it in terms of the file rather than the entry or field 
name? e.g. something like:
   
   > Within a snapshot, each content file must be referenced by at most one 
live entry across all manifests. Entries reference the same content file if 
they have the same file location, even if other field values differ. A snapshot 
in which more than one live entry references the same content file has 
undefined behavior. Writers are not required to validate uniqueness at commit 
time. 
   
   I dropped "because doing so can be expensive at commit time" because it 
might not belong to the spec, but we can retain it if you prefer. 



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