Clickhouse REGEXP: Exclude "service"

TODO: collapasable, copyable, download, etc

In a Clickhouse REGEXP, what would be the best way to form the reg ex to say I don't want. a string that matches service?In Clickhouse, when using regular expressions, you can specify that you do not want a certain pattern to match by using negative lookahead. Negative lookahead is a feature in regular expressions where you can specify a pattern that should not be followed by another pattern.

To create a regular expression in Clickhouse that matches strings not containing "service", you would use a pattern like this:

^(?!.*service).*

Here's what this pattern does:

1. ^ asserts the start of a line.
2. (?!.*service) is a negative lookahead assertion. It means "what follows should not be any number of characters followed by 'service'".
3. .* then matches any character (except for line terminators), zero or more times.

This regular expression will match any string that does not contain the substring "service". It's important to note that this is case-sensitive. If you want to make it case-insensitive, you would use a flag or a different pattern depending on the capabilities of the regex engine in Clickhouse.clickhouse regex engine is re2 which doesn't support ?!You're correct that ClickHouse uses the RE2 regex engine, which indeed does not support lookahead or lookbehind assertions. In this case, you would typically approach the problem differently since you can't directly express "not containing a specific substring" in a single regular expression using RE2.

However, you can achieve the desired result by using ClickHouse's match function in combination with a conditional to filter out rows containing the unwanted pattern. Here's an approach:

1. Use the match function to find rows that contain the string service.
2. Use a NOT condition to exclude these rows.

Here's an example query demonstrating this approach:

SELECT *
FROM your_table
WHERE NOT match(your_column, 'service')

This query selects all rows from your_table where your_column does not contain the string 'service'. The match function returns 1 (true) if the pattern is found, and 0 (false) otherwise. By using NOT, you exclude the rows where the pattern is found.Is there a NOT that works with REGEXP syntax of clickhouse?In ClickHouse, when using regular expressions with the REGEXP or match function, there isn't a direct way to invert the match within the regular expression syntax itself, as RE2 (the engine used by ClickHouse) does not support negative lookahead or lookbehind. However, you can achieve the effect of a "NOT" operation by using ClickHouse's SQL logic outside of the regular expression.

You can do this by using the NOT operator in combination with the match function in a WHERE clause. The match function returns 1 (true) if the string matches the pattern, and 0 (false) otherwise. By using NOT, you effectively invert this logic.

Here's an example:

SELECT *
FROM your_table
WHERE NOT match(your_column, 'service')

In this query, your_column is the column you're checking, and your_table is your table. This will select rows where your_column does not contain the string 'service'.

Another approach, if you want to use REGEXP, is to use the NOT operator outside the regular expression:

SELECT *
FROM your_table
WHERE your_column NOT REGEXP 'service'

Both methods are functionally equivalent in this context and will filter out rows where the column contains the string 'service'.What is idiomatic JS for declaring a new list that has a copy of an already existing list and adding two items?In modern JavaScript, a common and idiomatic way to create a new list (array) that includes the contents of an existing array, plus additional items, is to use the spread operator (...). The spread operator allows an iterable such as an array to be expanded in places where zero or more arguments or elements are expected.

Here is an example:

const existingList = [1, 2, 3]; // This is your existing list
const newItem1 = 4;             // First new item to add
const newItem2 = 5;             // Second new item to add

const newList = [...existingList, newItem1, newItem2];

In this example, newList will be a new array that contains all the elements of existingList, followed by newItem1 and newItem2. This method is clean, readable, and concise, and it leverages the immutability concept by not modifying the original existingList.

Clickhouse REGEXP: Exclude "service" created at Tue Jan 20 1970 18:02:33 GMT+0000 (Coordinated Universal Time)