mirror of
https://github.com/ClickHouse/ClickHouse.git
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67c2e50331
* 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 * Lost blank lines * Add new logo sizes * update presentations * Next step in migrating to new documentation * Fix all warnings in en reference * Fix all warnings in ru reference * Re-arrange existing reference * Move operation tips to main reference * Fix typos noticed by milovidov@ * Get rid of zookeeper.md * Looks like duplicate of tutorial.html * Fix some mess with html tags in tutorial * No idea why nobody noticed this before, but it was completely not clear whet to get the data * Match code block styling between main and tutorial pages (in favor of the latter) * Get rid of some copypaste in tutorial * Normalize header styles * Move example_datasets to sphinx * Move presentations submodule to website * Move and update README.md * No point in duplicating articles from habrahabr here * Move development-related docs as is for now * doc/reference/ -> docs/ (to match the URL on website) * Adapt links to match the previous commit * Adapt development docs to rst (still lacks translation and strikethrough support) * clean on release * blacklist presentations in gulp * strikethrough support in sphinx * just copy development folder for now * fix weird introduction in style article * Style guide translation (WIP) * Finish style guide translation to English * gulp clean separately * Update year in LICENSE * Initial CONTRIBUTING.md * Fix remaining links to old docs in tutorial * Some tutorial fixes * Typo * Another typo * Update list of authors from yandex-team accoding to git log
282 lines
10 KiB
ReStructuredText
282 lines
10 KiB
ReStructuredText
Other functions
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---------------
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hostName()
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~~~~~~~~~~
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Returns a string with the name of the host that this function was performed on. For distributed processing, this is the name of the remote server host, if the function is performed on a remote server.
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visibleWidth(x)
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~~~~~~~~~~~~~~~
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Calculates the approximate width when outputting values to the console in text format (tab-separated). This function is used by the system for implementing Pretty formats.
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toTypeName(x)
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~~~~~~~~~~~~~
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Gets the type name. Returns a string containing the type name of the passed argument.
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blockSize()
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~~~~~~~~~~~
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Gets the size of the block.
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In ClickHouse, queries are always run on blocks (sets of column parts). This function allows getting the size of the block that you called it for.
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materialize(x)
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~~~~~~~~~~~~~~
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Turns a constant into a full column containing just one value.
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In ClickHouse, full columns and constants are represented differently in memory. Functions work differently for constant arguments and normal arguments (different code is executed), although the result is almost always the same. This function is for debugging this behavior.
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ignore(...)
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~~~~~~~~~~~
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A function that accepts any arguments and always returns 0.
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However, the argument is still calculated. This can be used for benchmarks.
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sleep(seconds)
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~~~~~~~~~~~~~~
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Sleeps 'seconds' seconds on each data block. You can specify an integer or a floating-point number.
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currentDatabase()
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~~~~~~~~~~~~~~~~~
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Returns the name of the current database.
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You can use this function in table engine parameters in a CREATE TABLE query where you need to specify the database..
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isFinite(x)
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~~~~~~~~~~~
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Accepts Float32 and Float64 and returns UInt8 equal to 1 if the argument is not infinite and not a NaN, otherwise 0.
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isInfinite(x)
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~~~~~~~~~~~~~
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Accepts Float32 and Float64 and returns UInt8 equal to 1 if the argument is infinite, otherwise 0.
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Note that 0 is returned for a NaN
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isNaN(x)
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~~~~~~~~
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Accepts Float32 and Float64 and returns UInt8 equal to 1 if the argument is a NaN, otherwise 0.
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hasColumnInTable('database', 'table', 'column')
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Accepts constant String columns - database name, table name and column name. Returns constant UInt8 value, equal to 1 if column exists,
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otherwise 0.
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If table doesn't exist than exception is thrown.
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For elements of nested data structure function checks existence of column. For nested data structure 0 is returned.
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bar
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~~~
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Allows building a unicode-art diagram.
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``bar(x, min, max, width)`` - Draws a band with a width proportional to (x - min) and equal to 'width' characters when x == max.
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``min, max`` - Integer constants. The value must fit in Int64.
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``width`` - Constant, positive number, may be a fraction.
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The band is drawn with accuracy to one eighth of a symbol. Example:
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.. code-block:: sql
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SELECT
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toHour(EventTime) AS h,
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count() AS c,
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bar(c, 0, 600000, 20) AS bar
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FROM test.hits
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GROUP BY h
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ORDER BY h ASC
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.. code-block:: text
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┌──h─┬──────c─┬─bar────────────────┐
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│ 0 │ 292907 │ █████████▋ │
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│ 1 │ 180563 │ ██████ │
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│ 2 │ 114861 │ ███▋ │
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│ 3 │ 85069 │ ██▋ │
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│ 4 │ 68543 │ ██▎ │
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│ 5 │ 78116 │ ██▌ │
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│ 6 │ 113474 │ ███▋ │
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│ 7 │ 170678 │ █████▋ │
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│ 8 │ 278380 │ █████████▎ │
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│ 9 │ 391053 │ █████████████ │
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│ 10 │ 457681 │ ███████████████▎ │
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│ 11 │ 493667 │ ████████████████▍ │
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│ 12 │ 509641 │ ████████████████▊ │
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│ 13 │ 522947 │ █████████████████▍ │
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│ 14 │ 539954 │ █████████████████▊ │
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│ 15 │ 528460 │ █████████████████▌ │
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│ 16 │ 539201 │ █████████████████▊ │
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│ 17 │ 523539 │ █████████████████▍ │
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│ 18 │ 506467 │ ████████████████▊ │
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│ 19 │ 520915 │ █████████████████▎ │
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│ 20 │ 521665 │ █████████████████▍ │
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│ 21 │ 542078 │ ██████████████████ │
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│ 22 │ 493642 │ ████████████████▍ │
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│ 23 │ 400397 │ █████████████▎ │
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└────┴────────┴────────────────────┘
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transform
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~~~~~~~~~
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Transforms a value according to the explicitly defined mapping of some elements to other ones.
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There are two variations of this function:
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1. ``transform(x, array_from, array_to, default)``
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``x`` - What to transform
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``array_from`` - Constant array of values for converting.
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``array_to`` - Constant array of values to convert the values in 'from' to.
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``default`` - Constant. Which value to use if 'x' is not equal to one of the values in 'from'
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``'array_from'`` and ``'array_to'`` are arrays of the same size.
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Types:
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``transform(T, Array(T), Array(U), U) -> U``
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``'T'`` and ``'U'`` can be numeric, string, or Date or DateTime types.
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Where the same letter is indicated (T or U), for numeric types these might not be matching types, but types that have a common type.
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For example, the first argument can have the Int64 type, while the second has the Array(Uint16) type.
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If the 'x' value is equal to one of the elements in the 'array_from' array, it returns the existing element (that is numbered the same) from the 'array_to' array. Otherwise, it returns 'default'. If there are multiple matching elements in 'array_from', it returns one of the matches.
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Example:
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.. code-block:: sql
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SELECT
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transform(SearchEngineID, [2, 3], ['Яндекс', 'Google'], 'Остальные') AS title,
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count() AS c
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FROM test.hits
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WHERE SearchEngineID != 0
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GROUP BY title
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ORDER BY c DESC
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.. code-block:: text
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┌─title─────┬──────c─┐
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│ Яндекс │ 498635 │
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│ Google │ 229872 │
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│ Остальные │ 104472 │
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└───────────┴────────┘
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2. ``transform(x, array_from, array_to)``
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Differs from the first variation in that the 'default' argument is omitted.
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If the 'x' value is equal to one of the elements in the 'array_from' array, it returns the matching element (that is numbered the same) from the 'array_to' array. Otherwise, it returns 'x'.
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Types:
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``transform(T, Array(T), Array(T)) -> T``
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Example:
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.. code-block:: sql
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SELECT
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transform(domain(Referer), ['yandex.ru', 'google.ru', 'vk.com'], ['www.yandex', 'ввв.яндекс.рф', 'example.com']) AS s,
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count() AS c
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FROM test.hits
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GROUP BY domain(Referer)
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ORDER BY count() DESC
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LIMIT 10
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.. code-block:: text
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┌─s──────────────┬───────c─┐
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│ │ 2906259 │
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│ www.yandex │ 867767 │
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│ ███████.ru │ 313599 │
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│ mail.yandex.ru │ 107147 │
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│ ввв.яндекс.рф │ 105668 │
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│ ██████.ru │ 100355 │
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│ █████████.ru │ 65040 │
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│ news.yandex.ru │ 64515 │
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│ ██████.net │ 59141 │
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│ example.com │ 57316 │
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└────────────────┴─────────┘
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formatReadableSize(x)
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~~~~~~~~~~~~~~~~~~~~~
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Gets a size (number of bytes). Returns a string that contains rounded size with the suffix (KiB, MiB etc.).
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Example:
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.. code-block:: sql
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SELECT
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arrayJoin([1, 1024, 1024*1024, 192851925]) AS filesize_bytes,
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formatReadableSize(filesize_bytes) AS filesize
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.. code-block:: text
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┌─filesize_bytes─┬─filesize───┐
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│ 1 │ 1.00 B │
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│ 1024 │ 1.00 KiB │
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│ 1048576 │ 1.00 MiB │
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│ 192851925 │ 183.92 MiB │
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└────────────────┴────────────┘
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least(a, b)
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~~~~~~~~~~~
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Returns the least element of a and b.
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greatest(a, b)
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~~~~~~~~~~~~~~
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Returns the greatest element of a and b
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uptime()
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~~~~~~~~
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Returns server's uptime in seconds.
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version()
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~~~~~~~~~
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Returns server's version as a string.
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rowNumberInAllBlocks()
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~~~~~~~~~~~~~~~~~~~~~~
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Returns an incremental row number within all blocks that were processed by this function.
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runningDifference(x)
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~~~~~~~~~~~~~~~~~~~~
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Calculates the difference between consecutive values in the data block.
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Result of the function depends on the order of the data in the blocks.
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It works only inside of the each processed block of data. Data splitting in the blocks is not explicitly controlled by the user.
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If you specify ``ORDER BY`` in subquery and call runningDifference outside of it, you could get an expected result.
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Example:
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.. code-block:: sql
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SELECT
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EventID,
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EventTime,
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runningDifference(EventTime) AS delta
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FROM
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(
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SELECT
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EventID,
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EventTime
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FROM events
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WHERE EventDate = '2016-11-24'
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ORDER BY EventTime ASC
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LIMIT 5
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)
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.. code-block:: text
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┌─EventID─┬───────────EventTime─┬─delta─┐
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│ 1106 │ 2016-11-24 00:00:04 │ 0 │
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│ 1107 │ 2016-11-24 00:00:05 │ 1 │
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│ 1108 │ 2016-11-24 00:00:05 │ 0 │
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│ 1109 │ 2016-11-24 00:00:09 │ 4 │
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│ 1110 │ 2016-11-24 00:00:10 │ 1 │
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└─────────┴─────────────────────┴───────┘
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MACNumToString(num)
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~~~~~~~~~~~~~~~~~~~
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Takes a UInt64 number. Interprets it as an MAC address in big endian. Returns a string containing the corresponding MAC address in the format AA:BB:CC:DD:EE:FF (colon-separated numbers in hexadecimal form).
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MACStringToNum(s)
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~~~~~~~~~~~~~~~~~
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The reverse function of MACNumToString. If the MAC address has an invalid format, it returns 0.
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MACStringToOUI(s)
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~~~~~~~~~~~~~~~~~
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Takes MAC address in the format AA:BB:CC:DD:EE:FF (colon-separated numbers in hexadecimal form). Returns first three octets as UInt64 number. If the MAC address has an invalid format, it returns 0.
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