Alexey Milovidov alexey-milovidov
alexey-milovidov
/ example.txt
Created
August 28, 2017 18:09
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| :) SELECT number % 3 AS key, number AS x FROM system.numbers LIMIT 10 | |
| SELECT | |
| number % 3 AS key, | |
| number AS x | |
| FROM system.numbers | |
| LIMIT 10 | |
| ┌─key─┬─x─┐ | |
| │ 0 │ 0 │ |
alexey-milovidov
/ concurrent_sessions_example..txt
Created
September 5, 2017 00:14
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| :) CREATE TABLE test.sessions (begin DateTime, end DateTime) ENGINE = Memory | |
| CREATE TABLE test.sessions | |
| ( | |
| begin DateTime, | |
| end DateTime | |
| ) ENGINE = Memory | |
| Ok. |
alexey-milovidov
/ asan.txt
Created
September 7, 2017 03:38
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| ================================================================= | |
| ==260044:302867==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61500060db01 at pc 0x00000cf8e0a5 bp 0x7f0359a478f0 sp 0x7f0359a478e8 | |
| WRITE of size 8 at 0x61500060db01 thread T3436 | |
| #0 0xcf8e0a4 (/usr/bin/clickhouse+0xcf8e0a4) | |
| #1 0xcf8e42b (/usr/bin/clickhouse+0xcf8e42b) | |
| #2 0xcf8f39f (/usr/bin/clickhouse+0xcf8f39f) | |
| #3 0xcf8f78c (/usr/bin/clickhouse+0xcf8f78c) | |
| #4 0xcdef1df (/usr/bin/clickhouse+0xcdef1df) | |
| #5 0xcddf6af (/usr/bin/clickhouse+0xcddf6af) | |
| #6 0xcde32bb (/usr/bin/clickhouse+0xcde32bb) |
alexey-milovidov
/ tableau.txt
Last active
July 24, 2018 14:30
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| Как настроить Tableau over ClickHouse ODBC на Windows | |
| ==== ODBC-драйвер для Clickhouse | |
| 1. Надо поставить драйвер https://github.com/yandex/clickhouse-odbc/releases/latest | |
| 2. Создать источник данных odbc. Пример: | |
| https://dev.mysql.com/doc/connector-odbc/en/connector-odbc-configuration-dsn-windows-5-2.html | |
| Надо выбрать Unicode версию odbc-драйвера |
alexey-milovidov
/ intern_tasks.txt
Last active
September 30, 2021 01:23
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| 1. Short-curcuit вычисление некоторых функций. | |
| ClickHouse использует векторное вычисление выражений в запросах (vectorized query execution). То есть, каждая функция вызывается не для отдельных значений, а для небольших массивов - кусочков столбцов. Для примера, в вычисление x + y будут переданы два массива - массив значений x и массив соответствующих значений y. | |
| Недостаток состоит в том, что сложнее реализовать short-curcuit операторы. К таким операторам относятся AND, OR, if. Для примера, в выражении expr1 AND expr2, будут сначала вычислены оба аргумента, а затем переданы в функцию AND. Хотя в тех строчках, где expr1 равно false, выражение expr2 вовсе не обязательно было вычислять. Это становится проблемой, когда само вычисление expr2 сложное, или когда при вычислении expr2 может быть выкинуто исключение. | |
| Short-curcuit вычисление можно было бы реализовать так: | |
| - вычислить expr1; | |
| - отфильтровать массивы входных аргументов для вычисления expr2, оставив только значения, где expr1 = true; | |
| - вычислить expr2 на |
alexey-milovidov
/ float_parsing_comparison.txt
Created
January 12, 2018 01:36
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| Old: | |
| Running: float_parsing | |
| [ | |
| { | |
| "hostname": "", | |
| "main_metric": "avg_rows_per_second", | |
| "num_cores": 16, | |
| "num_threads": 32, | |
| "parameters": { |
alexey-milovidov
/ unsorted_tasks.txt
Last active
September 30, 2021 01:21
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| + - сделано хотя бы в master | |
| * - в процессе | |
| Доработки форматов. | |
| + Protobuf | |
| + Parquet | |
| + Avro | |
| + Настраиваемое поведение CSV: separator. |
alexey-milovidov
/ gist:af93e87433a23181a86556ca85dbc289
Created
March 26, 2018 03:01
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| ClickHouse client version 1.1.54371. | |
| Connecting to localhost:9000. | |
| Connected to ClickHouse server version 1.1.54371. | |
| localhost :) USE test | |
| USE test | |
| Ok. |
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| $ echo '[1, -1]' | clickhouse-local -S 'x Array(UInt8)' --query="SELECT * FROM table" | |
| Code: 130, e.displayText() = DB::Exception: Cannot read array from text: (at row 1) | |
| Row 1: | |
| Column 0, name: x, type: Array(UInt8), parsed text: "[1, "ERROR | |
| , e.what() = DB::Exception (from 0.0.0.0:0) (in query: SELECT * FROM table), Stack trace: | |
| 0. clickhouse-local(StackTrace::StackTrace()+0x12) [0x53d67b2] | |
| 1. clickhouse-local(DB::DataTypeArray::deserializeText(DB::IColumn&, DB::ReadBuffer&) const+0x2a4) [0x7e69cb4] |
alexey-milovidov
/ forest_in_sql.sql
Created
May 6, 2018 09:57
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| SELECT user_id, arrayReduce('sum',[if(f21<0.287376, if(f2<-1.34168, if(f21<-0.0465033, -0.0411413, -0.0168165), if(f18<0.0541038, -0.0486026, -0.0432873)), if(f2<-1.12007, if(f19<0.514323, -0.00154215, 0.0279125), if(f23<-0.0269176, -0.0391427, -0.0148464))),if(f21<0.287376, if(f2<-1.30474, if(f21<-0.0465033, -0.0407256, -0.0184058), if(f23<-0.0274336, -0.0469912, -0.0290771)), if(f2<-1.157, if(f23<-0.027484, -0.00114219, 0.029407), if(f2<-0.344426, -0.0242555, -0.0423453))),if(f18<0.883746, if(f2<-1.34168, if(f21<-0.00940569, -0.0386349, -0.00968768), if(f23<-0.0274894, -0.0458335, -0.0281316)), if(f2<-1.30474, if(f23<-0.0273632, -0.00346079, 0.0302068), if(f19<0.514323, -0.0340366, -0.00648281))),if(f21<0.250278, if(f2<-1.34168, if(f21<-0.0465033, -0.0383863, -0.0166084), if(f18<0.0541038, -0.0453193, -0.0402171)), if(f2<-1.30474, if(f22<0.233904, 0.00176162, 0.0268355), if(f2<-0.639908, -0.0178382, -0.0385038))),if(f18<0.607199, if(f2<-1.34168, if(f21<-0.00940569, -0.0373913, -0.0101554), if(f23<-0.0274336 |