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Merge pull request #4225 from ethereum/fixeventtopics

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Clarify events.
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Alex Beregszaszi 2018-06-19 19:00:30 +01:00 committed by GitHub
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1 changed files with 8 additions and 12 deletions
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docs/contracts.rst
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@ -723,22 +723,18 @@ the contract can only see the last 256 block hashes.
Up to three parameters can
receive the attribute ``indexed`` which will cause the respective arguments
to be searched for: It is possible to filter for specific values of
indexed arguments in the user interface.
If arrays (including ``string`` and ``bytes``) are used as indexed arguments, the
Keccak-256 hash of it is stored as topic instead.
The hash of the signature of the event is one of the topics except if you
to be stored in a special data structure as so-called "topics", which allows them to be searched for,
for example when filtering a sequence of blocks for certain events. Events can always
be filtered by the address of the contract that emitted the event. Also,
the hash of the signature of the event is one of the topics except if you
declared the event with ``anonymous`` specifier. This means that it is
not possible to filter for specific anonymous events by name.
All non-indexed arguments will be stored in the data part of the log.
If arrays (including ``string`` and ``bytes``) are used as indexed arguments, the
Keccak-256 hash of it is stored as topic instead. This is because a topic
can only hold a single word (32 bytes).
.. note::
Indexed arguments will not be stored themselves. You can only
search for the values, but it is impossible to retrieve the
values themselves.
All non-indexed arguments will be :ref:`ABI-encoded <ABI>` into the data part of the log.
::