64 lines
2.2 KiB
Markdown
64 lines
2.2 KiB
Markdown
|
## Differences
|
||
|
|
|
||
|
|
Although we try to implement openCypher query language as closely to the
|
||
|
|
language reference as possible, we had to make some changes to enhance the
|
||
|
|
user experience.
|
||
|
|
|
||
|
|
### Symbolic Names
|
||
|
|
|
||
|
|
We don't allow symbolic names (variables, label names...) to be openCypher
|
||
|
|
keywords (WHERE, MATCH, COUNT, SUM...).
|
||
|
|
|
||
|
|
### Unicode Codepoints in String Literal
|
||
|
|
|
||
|
|
Use `\u` followed by 4 hex digits in string literal for UTF-16 codepoint and
|
||
|
|
`\U` with 8 hex digits for UTF-32 codepoint in Memgraph.
|
||
|
|
|
||
|
|
|
||
|
|
### Difference from Neo4j's Cypher Implementation
|
||
|
|
|
||
|
|
The openCypher initiative stems from Neo4j's Cypher query language. Following is a list
|
||
|
|
of most important differences between Neo's Cypher and Memgraph's openCypher implementation,
|
||
|
|
for users that are already familiar with Neo4j. There might be other differences not documented
|
||
|
|
here (especially subtle semantic ones).
|
||
|
|
|
||
|
|
#### Unsupported Constructs
|
||
|
|
|
||
|
|
* Data importing. Memgraph doesn't support Cypher's CSV importing capabilities.
|
||
|
|
* The `FOREACH` language construct for performing an operation on every list element.
|
||
|
|
* The `CALL` construct for a standalone function call. This can be expressed using
|
||
|
|
`RETURN functioncall()`. For example, with Memgraph you can get information about
|
||
|
|
the indexes present in the database using the `RETURN indexinfo()` openCypher query.
|
||
|
|
* Stored procedures.
|
||
|
|
* Regular expressions for string matching.
|
||
|
|
* `shortestPath` and `allShortestPaths` functions. `shortestPath` can be expressed using
|
||
|
|
Memgraph's breadth-first expansion syntax already described in this document.
|
||
|
|
* Patterns in expressions. For example, Memgraph doesn't support `size((n)-->())`. Most of the time
|
||
|
|
the same functionalities can be expressed differently in Memgraph using `OPTIONAL` expansions,
|
||
|
|
function calls etc.
|
||
|
|
* Map projections such as `MATCH (n) RETURN n {.property1, .property2}`.
|
||
|
|
|
||
|
|
#### Unsupported Functions
|
||
|
|
|
||
|
|
General purpose functions:
|
||
|
|
|
||
|
|
* `exists(n.property)` - This can be expressed using `n.property IS NOT NULL`.
|
||
|
|
* `length()` is named `size()` in Memgraph.
|
||
|
|
|
||
|
|
Aggregation functions:
|
||
|
|
|
||
|
|
* `count(DISTINCT variable)` - This can be expressed using `WITH DISTINCT variable RETURN count(variable)`.
|
||
|
|
|
||
|
|
Mathematical functions:
|
||
|
|
|
||
|
|
* `percentileDisc()`
|
||
|
|
* `stDev()`
|
||
|
|
* `point()`
|
||
|
|
* `distance()`
|
||
|
|
* `degrees()`
|
||
|
|
|
||
|
|
List functions:
|
||
|
|
|
||
|
|
* `any()`
|
||
|
|
* `none()`
|