RussellSpitzer commented on code in PR #17198:
URL: https://github.com/apache/iceberg/pull/17198#discussion_r3582389206


##########
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:
   I'm trying to write this in a way in that no one actually has to validate 
uniqueness. 
   
   But you should be doing what you can to guarantee you are writing unique 
paths. A writer that names all it's files "foo.parquet" would be obviously 
noncompliant, or a writer that names all it's files "fileN.parquet" where N is 
a number starting at 0 per process, would also be broken. The statement here is 
more of a way to clearly be able to have something to point to and say "this 
implementation is broken"



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