Reference Functions Reference
Reference Functions
The REFERENCE
type acts as a "pointer" to other documents in the database (or
even other databases). The following functions allow manipulating this type
during query execution.
| Name | Description |
COLLECTION_ID
|
Returns the ID of the leaf collection in the given reference |
DOCUMENT_ID
|
Returns the ID of the document in the given reference |
PARENT
|
Returns the parent reference |
REFERENCE_SLICE
|
Returns a subset of segments from the given reference |
COLLECTION_ID
Syntax:
collection_id(ref: REFERENCE) -> STRING
Description:
Returns the leaf collection ID of the given REFERENCE
.
Examples:
ref
|
collection_id(ref)
|
|---|---|
users/user1
|
"users"
|
users/user1/posts/post1
|
"posts"
|
DOCUMENT_ID
Syntax:
document_id(ref: REFERENCE) -> ANY
Description:
Returns the document ID of the given REFERENCE
.
Examples:
ref
|
document_id(ref)
|
|---|---|
users/user1
|
"user1"
|
users/user1/posts/post1
|
"post1"
|
PARENT
Syntax:
parent(ref: REFERENCE) -> REFERENCE
Description:
Returns the parent REFERENCE
of the given reference, or NULL
if the ref is
a root reference already.
Examples:
ref
|
parent(ref)
|
|---|---|
/
|
NULL
|
users/user1
|
/
|
users/user1/posts/post1
|
users/user1
|
REFERENCE_SLICE
Syntax:
reference_slice(ref: REFERENCE, offset: INT, length: INT) -> REFERENCE
Description:
A REFERENCE
is a list of (collection_id, document_id)
tuples and this allows
getting a view of that list, just like array_slice(...)
.
Returns a new REFERENCE
that is a subset of the segments of the given ref
.
-
offset: The starting index (0-based) of the slice. If negative, it is an offset from the end of the reference. -
length: The number of segments to include in the slice.
Examples:
ref
|
offset
|
length
|
reference_slice(ref, offset, length)
|
|---|---|---|---|
a/1/b/2/c/3
|
1L | 2L | b/2/c/3
|
a/1/b/2/c/3
|
0L | 2L | a/1/b/2
|
a/1/b/2/c/3
|
-2L | 2L | c/3
|
What's next
- See the Pipeline Queries overview
