Can't hash a map

kindlychung · 13 April 2021 20:30

Here is the code:

//int hash() | Takes in any data type and encodes it into an integer value. |
return hash({key: 'Value', listKey: [{inner: 'Map1'}, {inner: 'Map2'}]})

Error:

[ERROR (-12)]: SemanticError: `hash({key:"Value",listKey:[{inner:"Map1"},{inner:"Map2"}]})' is not a valid expression : Parameter's type error

RandomJoe · 14 April 2021 01:36

Hi there! The hash() function cannot hash a map. For what it can do, see the hash doc.

RandomJoe · 14 April 2021 01:38

If you need to hash maps, could you please submit an issue and share your scenario?

dingding · 14 April 2021 01:42

The hash function only supported int/float/string/bool/date/datetime/path/vertex/edge/list/NULL. Just the MAP and SET is not supported.

kindlychung · 14 April 2021 20:52

I don’t have a clear use case for hashing maps yet, will submit an issue once I do.

The documentation is not accurate here:

github.com

vesoft-inc/nebula-docs/blob/4a2966e60fd694f0b550b176e56ef80fd4ebe9ab/docs-2.0/3.ngql-guide/6.functions-and-expressions/2.string.md#L26


      
          string left(string a, int count) | Returns the substring in [1, count], if length a is less than count, Returns a. |
          string right(string a, int count) | Returns the substring in [size - count + 1, size], if length a is less than count, Returns a. |
          string lpad(string a, int size, string letters) | Left-pads a string with another string to a certain length.|
          string rpad(string a, int size, string letters)| Reft-pads a string with another string to a certain length.  |
          string substr(string a, int pos, int count) | Returns a substring from a string, starting at the specified position `pos`, extract `count` characters. |
          string substring(string a, int pos, int count) | The same as substr(). |
          string reverse(string) | Returns the reverse of a string.
          string replace(string a, string b, string c) | Replaces string b in string a with string c.
          list split(string a, string b) | Splits string a at string b and returns a list of strings.
          string toString() | Takes in any data type and converts it into a string.
          int hash() | Takes in any data type and encodes it into an integer value. |
          
          
> **NOTE**: If the argument is `NULL`, the return is undefined.
          
          
## Explanations for the return of `substr()` and `substring()`
          
          
- `pos` uses a 0-based index.
          - If `pos` is 0, the whole string `a` is returned.
          - If `pos` is greater than the maximum string index, an empty string is returned.
          - If `pos` is a negative number, `BAD_DATA` is returned.
          - If `count` is omitted, the function returns the substring starting at the position given by `pos` and

dingding · 15 April 2021 01:23

Thanks for your feedback. We will modify the document as soon as possible.

jamieliu1023 · 15 April 2021 01:23

@RandomJoe