14.9.1 Syntax
Trivial Expressions
Always evaluates to true
:
true
Always evaluates to false
:
false
Constants
Legal constants are integer, long and floating point numbers of single and double precision as well as strings literals and true
and false
. Long constants need to be suffixed with l
or L
. Floating point numbers are treated as double precision numbers by default. To force a certain precision you can use f
or F
for single precision and d
or D
for double precision floating point numbers. String literals are UTF-8 character sequences, surrounded by single or double quotation marks.
25
4294967296L
0.62f
0.33d
"Double quoted string"
'Single quoted string'
Vertex and Edge Identifiers
Depending on the filter type, different identifiers are valid.
Vertex Filter
Vertex filter expressions have only one keyword that addresses the vertex in the current context.
vertex
denotes the vertex that is currently being evaluated by the filter expression.
vertex
Edge Filter
Edge filter expressions have several keywords that addresses the edge or its vertices in the current context.
edge
denotes the edge that is currently being evaluated by the filter expression.
edge
dst
denotes the destination vertex of the current edge. dst
is only valid in the subgraph context.
dst
src
denotes the source vertex of the current edge. src
is only valid in the subgraph context.
src
Properties
Filter expressions can access the values of vertex and edge properties.
<id>.<property>
where:
<id>:
is any vertex or edge identifier (that is,src
,dst
,vertex
,edge
).<property>:
is the name of a vertex or edge property.Note:
This has to be the name of an edge property if the identifier isedge
. Otherwise it has to be a vertex property.
If the property name is a reserved name in the filter expression syntax or contains spaces, it must be quoted in single or double quotes.
The following code accesses the 'cost' property of the source vertex.
src.cost
Temporal properties support values comparison (constants and property values) using special constructors. The default temporal formats are shown in the following table:
Table 14-4 Default Temporal Formats
Property Type | Constructor |
---|---|
DATE |
date ('yyyy-MM-dd HH:mm:ss') |
LOCAL_DATE |
date 'yyyy-MM-dd' |
TIME |
time 'HH:mm:ss' |
TIME_WITH_TIMEZONE |
time 'HH:mm:ss+/-XXX' |
TIMESTAMP |
timestamp 'yyyy-MM-dd HH:mm:ss' |
TIMESTAMP_WITH_TIMEZONE |
timestamp 'yyyy-MM-dd HH:mm:ss+/-XXX' |
The following expression accesses the property 'timestamp_withTZ
' of an edge and checks if it is equal to 3/27/2007 06:00+01:00
.
edge.timestamp_withTZ = timestamp'2007-03-2706:00:00+01:00'
Note:
Properties of type date can only be checked for equality. date type usage is deprecated since version 2.5, instead use local date or timestamp types that support all operations.Methods
Filter expressions support the following functions:
Degree Functions
outDegree()
returns the number of outgoing edges of the vertex identifier.degree()
is a synonym foroutDegree
.int <id>.degree() int <id>.outDegree()
The following example determines whether the
out-degree
of the source vertex is greater than three:src.degree() > 3
inDegree()
returns the number of incoming edges of the vertex identifier.int <id>.inDegree()
Label Functions
hasLabel()
checks if a vertex has a label.boolean <id>.hasLabel('<label>')
The following example determines whether a vertex has the label "
city
":vertex.hasLabel('city')
label()
returns the label of an edge.string <id>.label()
The following expression checks whether the label of an edge is "
clicked_by
":edge.label() = 'clicked_by'
Relational Expressions
To compare values (e.g., property values or constants), filter expressions provide the comparison operators listed below. Note: Both ==
and =
are synonyms.
== = != < <= > >=
The following example checks whether the "cost" property of the source vertex is lower than or equals to 1.23.
src.cost <= 1.23
Vertex ID Comparison
It is also possible to filter for vertices with a specific vertex ID.
<id> = <vertex_id>
The following example determines whether the source vertex of an edge has the vertex ID "San Francisco
"
src = "San Francisco"
Regular Expressions
Strings can be matched using regular expressions.
<string expression> =~ '<regularexpression>'
The following example checks if the edge label starts with a lowercase letter and ends with a number:
edge.label() =~ '^[a-z].*[0-9]$'
Note:
The syntax followed for the pattern on the right-hand side, is Java REGEX.Type Conversions
The following syntax allows converting the type of <expression>
to <type>
.
(<type>) <expression>
The following example converts the value of the 'cost
' property of the source vertex to an integer value:
(int) src.cost
Boolean Expressions
&&
(and), ||
(or) and !
(not).
Note:
Only boolean operands can be composed.(! true) || false edge.cost < INF && dst.visited = false src.degree() < 10 || !(dst.visited)
Arithmetic Expressions
+
, -
, *
, /
, %
.
Note:
These operators only work on numeric operands.1 + 5 -vertex.degree() edge.cost * 2 > 5 src.value * 2.5 = (dst.inDegree() + 5) / dst.outDegree()
Operator Precedence
Operator precedences are shown in the following list, from highest precedence to the lowest. An operator on a higher level is evaluated before an operator on a lower level.
+
(unary plus),-
(unary minus)*
,/
,%
+
,-
=
,!=
,<
,>
,<=
,>=
,=~
NOT
AND
OR
Syntactic Sugar
both
and any
denote the source and destination vertex of the current edge. They can be used to express a condition that should be true
for both or at least either one of the two vertices. These keywords are only valid in an edge filter expression. To use them in a vertex filter results in a runtime type-checking exception.
both any
The filter expressions inside the following examples are equivalent:
both.property = 1 src.property = 1 && dst.property = 1
any.degree() > 1 src.degree() > 1 || dst.degree() > 1
Parent topic: Filter Expressions