Copilot commented on code in PR #3861:
URL: https://github.com/apache/avro/pull/3861#discussion_r3567380249
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lang/py/avro/io.py:
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@@ -832,23 +1016,37 @@ def read_map(self, writers_schema:
avro.schema.MapSchema, readers_schema: avro.s
The actual count in this case
is the absolute value of the count written.
"""
- read_items = {}
+ read_items: Dict[str, object] = {}
+ # Map keys are strings (>= 1 byte length prefix) plus the value.
+ min_bytes = 1 + _min_bytes_per_element(writers_schema.values)
+ zero_byte_limit, structural_limit = _collection_limits()
block_count = decoder.read_long()
while block_count != 0:
if block_count < 0:
block_count = -block_count
decoder.skip_long()
+ self._ensure_collection_available(decoder, len(read_items),
block_count, min_bytes, zero_byte_limit, structural_limit)
Review Comment:
`read_map()` passes `len(read_items)` into `_ensure_collection_available()`,
but `len(read_items)` counts only unique keys. Avro maps can legally contain
duplicate keys (later entries overwrite earlier ones), so this can undercount
the number of decoded key/value pairs and allow the structural limit to be
exceeded (especially for non-seekable decoders where the bytes-remaining check
can’t run). Track a separate cumulative `items_read` counter (like `skip_map()`
does) and use that for the limit check.
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