alternative

Example: Alternative References

For this example the following configuration is used:

; this example uses the ni plugin syntax
; 1. metadata
[rootkey/ref]
check/reference = recursive

[otherkey/newref]
check/reference = alternative

; 2. configuration data
rootkey/ref = ../otherkey

otherkey/ref = ../yetanotherkey
otherkey/newref = ../otherotherkey

otherotherkey/ref = ../nonexistent
otherotherkey/newref = ../mergekey

yetanotherkey/ref = ../mergekey
yetanotherkey/newref = ../nonexistent

mergekey/ref = ../finalkey
mergekey/newref = ../finalkey

finalkey = ""

We mount it by executing:

cat << EOF > alternative.ini
; this example uses the ni plugin syntax
; 1. metadata
[rootkey/ref]
check/reference = recursive

[otherkey/newref]
check/reference = alternative

; 2. configuration data
rootkey/ref = ../otherkey

otherkey/ref = ../yetanotherkey
otherkey/newref = ../otherotherkey

otherotherkey/ref = ../nonexistent
otherotherkey/newref = ../mergekey

yetanotherkey/ref = ../mergekey
yetanotherkey/newref = ../nonexistent

mergekey/ref = ../finalkey
mergekey/newref = ../finalkey

finalkey = ""
EOF

kdb mount alternative.ini user:/tests/reference/alternative ni reference

The file contains a specification, which marks user:/tests/reference/alternative/rootkey/ref as our root reference key and user:/tests/reference/alternative/otherkey/newref as an alternative reference.

The actual configuration contains then a structure which is processed by the plugin like follows:

1. user:/tests/reference/alternative/rootkey/ref is read and its reference validated.
2. user:/tests/reference/alternative/otherkey/ref is read and its reference validated.
3. user:/tests/reference/alternative/otherkey/newref is discovered as an alternative reference and stored for later.
4. user:/tests/reference/alternative/yetanotherkey/ref is read and its reference validated.
5. user:/tests/reference/alternative/mergekey/ref is read and its reference validated.
6. user:/tests/reference/alternative/finalkey does not contain a reference, so we stop here.
7. Processing of the alternative reference chain from user:/tests/reference/alternative/otherkey/newref starts.
8. user:/tests/reference/alternative/otherkey/newref is read and its reference validated.
9. user:/tests/reference/alternative/otherotherkey/newref is read and its reference validated.
10. user:/tests/reference/alternative/mergekey/newref is read and its reference validated.
11. user:/tests/reference/alternative/finalkey does not contain a reference, so we stop here.

The resulting reference graph looks like this:

As you can see, the plugin completely ignores user:/tests/reference/alternative/yetanotherkey/newref as well as user:/tests/reference/alternative/otherother/ref and in turn does not throw an error because user:/tests/reference/alternative/nonexistent does not exist. However, the plugin does still exhaustively check both of the alternative reference chains. If you want to prohibit this, you can set the metakey check/reference/restrict to an empty value on whichever key you want to be a leaf node in the graph.

After we are done we can unmount the example with:

kdb umount user:/tests/reference/alternative