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* update presentations * CLICKHOUSE-2936: redirect from clickhouse.yandex.ru and clickhouse.yandex.com * update submodule * lost files * CLICKHOUSE-2981: prefer sphinx docs over original reference * CLICKHOUSE-2981: docs styles more similar to main website + add flags to switch language links * update presentations * Less confusing directory structure (docs -> doc/reference/) * Minify sphinx docs too * Website release script: fail fast + pass docker hash on deploy * Do not underline links in docs * shorter * cleanup docker images * tune nginx config * CLICKHOUSE-3043: get rid of habrastorage links * Lost translation * CLICKHOUSE-2936: temporary client-side redirect * behaves weird in test * put redirect back * CLICKHOUSE-3047: copy docs txts to public too * move to proper file * remove old pages to avoid confusion * Remove reference redirect warning for now * Refresh README.md * Yellow buttons in docs * Use svg flags instead of unicode ones in docs * fix test website instance * Put flags to separate files * wrong flag * Copy Yandex.Metrica introduction from main page to docs * Yet another home page structure change, couple new blocks (CLICKHOUSE-3045) * Update Contacts section * CLICKHOUSE-2849: more detailed legal information * CLICKHOUSE-2978 preparation - split by files * More changes in Contacts block * Tune texts on index page * update presentations * One more benchmark * Add usage sections to index page, adapted from slides * Get the roadmap started, based on slides from last ClickHouse Meetup * CLICKHOUSE-2977: some rendering tuning * Get rid of excessive section in the end of getting started * Make headers linkable * CLICKHOUSE-2981: links to editing reference - https://github.com/yandex/ClickHouse/issues/849 * CLICKHOUSE-2981: fix mobile styles in docs * Ban crawling of duplicating docs * Open some external links in new tab * Ban old docs too * Lots of trivial fixes in english docs * Lots of trivial fixes in russian docs * Remove getting started copies in markdown * Add Yandex.Webmaster * Fix some sphinx warnings * More warnings fixed in english docs * More sphinx warnings fixed * Add code-block:: text * More code-block:: text * These headers look not that well * Better switch between documentation languages * merge use_case.rst into ya_metrika_task.rst * Edit the agg_functions.rst texts * Add lost empty lines
54 lines
2.6 KiB
ReStructuredText
54 lines
2.6 KiB
ReStructuredText
Functions for working with JSON.
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--------------------------------
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In Yandex.Metrica, JSON is passed by users as session parameters. There are several functions for working with this JSON. (Although in most of the cases, the JSONs are additionally pre-processed, and the resulting values are put in separate columns in their processed format.) All these functions are based on strong assumptions about what the JSON can be, but they try not to do anything.
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The following assumptions are made:
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#. The field name (function argument) must be a constant.
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#. The field name is somehow canonically encoded in JSON. For example, ``visitParamHas('{"abc":"def"}', 'abc') = 1``, but ``visitParamHas('{"\\u0061\\u0062\\u0063":"def"}', 'abc') = 0``
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#. Fields are searched for on any nesting level, indiscriminately. If there are multiple matching fields, the first occurrence is used.
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#. JSON doesn't have space characters outside of string literals.
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visitParamHas(params, name)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Checks whether there is a field with the 'name' name.
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visitParamExtractUInt(params, name)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Parses UInt64 from the value of the field named 'name'. If this is a string field, it tries to parse a number from the beginning of the string. If the field doesn't exist, or it exists but doesn't contain a number, it returns 0.
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visitParamExtractInt(params, name)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The same as for Int64.
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visitParamExtractFloat(params, name)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The same as for Float64.
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visitParamExtractBool(params, name)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Parses a true/false value. The result is UInt8.
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visitParamExtractRaw(params, name)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Returns the value of a field, including separators.
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Examples:
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.. code-block:: text
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visitParamExtractRaw('{"abc":"\\n\\u0000"}', 'abc') = '"\\n\\u0000"'
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visitParamExtractRaw('{"abc":{"def":[1,2,3]}}', 'abc') = '{"def":[1,2,3]}'
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visitParamExtractString(params, name)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Parses the string in double quotes. The value is unescaped. If unescaping failed, it returns an empty string.
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Examples:
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.. code-block:: text
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visitParamExtractString('{"abc":"\\n\\u0000"}', 'abc') = '\n\0'
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visitParamExtractString('{"abc":"\\u263a"}', 'abc') = '☺'
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visitParamExtractString('{"abc":"\\u263"}', 'abc') = ''
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visitParamExtractString('{"abc":"hello}', 'abc') = ''
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Currently, there is no support for code points not from the basic multilingual plane written in the format ``\uXXXX\uYYYY`` (they are converted to CESU-8 instead of UTF-8).
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