Path-scoped projection
Like the path-scoped predicate, the path-scoped projection is a tool for limiting the search to find more relevant information without losing the relationships between different pieces of information.
- Example 1: Projecting the path through the SELECT clause
- Example 2: Fetching history with path-scoped projection
- Example 3: Losing relationships between data
- Example 4: Limiting searches at the wrong node
- Example 5: Limiting searches at the right node
- Example 6: Abbreviating the projected path
Example 1: Projecting the path through the SELECT clause
A simple example of a path-scoped projection is the following query where
the path projects through — or restricts — the SELECT
clause:
SELECT interface/(mac_address, name) FROM /network/device
This query finds the name and MAC address of each interface on every device on the network. When run against the sample database, this query returns the following results:
row
interface/(mac_address, name)
item
mac_address 01:01:02:03:04:05
name eth0
row
interface/(mac_address, name)
item
mac_address 02:A1:A2:A3:A4:A4
name eth0
item
mac_address 03:A1:A2:A3:A4:A5
name eth1
row
interface/(mac_address, name)
item
mac_address 04:A1:A2:A3:A4:A8
name eth0
item
mac_address 05:A1:A2:A3:A4:A9
name eth1
row
interface/(mac_address, name)
item
mac_address 06:13:72:F3:0A:F5
name eth0
item
mac_address 07:13:72:F3:0A:F6
name eth1
row
interface/(mac_address, name)
item
mac_address 08:16:CB:FF:FE:66
name eth0
item
mac_address 09:16:CB:FF:FE:67
name eth1
item
mac_address 10:16:CB:FF:FE:68
name eth2
item
mac_address 11:16:CB:FF:FE:69
name eth3
row
interface/(mac_address, name)
item
mac_address 12:10:D8:99:2B:C2
name eth0
item
mac_address 13:10:D8:99:2B:C1
name eth1
Example 2: Fetching history with path-scoped projection
In a second example of path-scoped projection, the query fetches the revision history of the name and MAC address of interfaces, and outputs the history per interface:
SELECT interface/(name, mac_address#history) FROM /network/device
Here is a view of part of the results of this query when run against the sample database:
row
interface/(name, history(mac_address))
item
name eth0
history
when 2008-04-06T00:21:52.518887Z
mac_address null
history
when 2008-04-06T07:33:52.518887Z
mac_address null
history
when 2008-04-06T14:45:52.518887Z
mac_address null
history
when 2008-04-06T21:57:52.518887Z
mac_address null
history
when 2008-04-07T05:09:52.518887Z
mac_address null
history
when 2008-04-07T12:21:52.518887Z
mac_address null
. . .
Example 3: Losing relationships between data
Similar to the path-scoped predicate, you run into trouble if you request the same information this way:
SELECT interface/mac_address, interface/name FROM /network/device
This query fetches the MAC address of each interface on each device, and the name of each interface on each device, but the resulting output does not reflect the relationship between the MAC address and name. When run against the sample database, this query returns the following uncorrelated results:
row
interface/mac_address 01:01:02:03:04:05
interface/name eth0
row
interface/mac_address
mac_address 02:A1:A2:A3:A4:A4
mac_address 03:A1:A2:A3:A4:A5
interface/name
name eth0
name eth1
row
interface/mac_address
mac_address 04:A1:A2:A3:A4:A8
mac_address 05:A1:A2:A3:A4:A9
interface/name
name eth0
name eth1
row
interface/mac_address
mac_address 06:13:72:F3:0A:F5
mac_address 07:13:72:F3:0A:F6
interface/name
name eth0
name eth1
row
interface/mac_address
mac_address 08:16:CB:FF:FE:66
mac_address 09:16:CB:FF:FE:67
mac_address 10:16:CB:FF:FE:68
mac_address 11:16:CB:FF:FE:69
interface/name
name eth0
name eth1
name eth2
name eth3
row
interface/mac_address
mac_address 12:10:D8:99:2B:C2
mac_address 13:10:D8:99:2B:C1
interface/name
name eth0
name eth1
So instead of writing SELECT interface/mac_address, interface/name,
use a path-scoped projection by writing SELECT interface/(mac_address,
name) to get correlated results as in
Example 1.
Example 4: Limiting searches at the wrong node
You might also retain the relationship discussed in
Example 3
by limiting the selection in the FROM
clause like this:
SELECT mac_address, name FROM /network/device/interface
When run against the sample database, this query returns correlated results, but much more limited than those of Example 1:
row mac_address 01:01:02:03:04:05 name eth0 row mac_address 02:A1:A2:A3:A4:A4 name eth0 row mac_address 03:A1:A2:A3:A4:A5 name eth1 row mac_address 04:A1:A2:A3:A4:A8 name eth0 row mac_address 05:A1:A2:A3:A4:A9 name eth1 row mac_address 06:13:72:F3:0A:F5 name eth0 row mac_address 07:13:72:F3:0A:F6 name eth1 row mac_address 08:16:CB:FF:FE:66 name eth0 row mac_address 09:16:CB:FF:FE:67 name eth1 row mac_address 10:16:CB:FF:FE:68 name eth2 row mac_address 11:16:CB:FF:FE:69 name eth3 row mac_address 12:10:D8:99:2B:C2 name eth0 row mac_address 13:10:D8:99:2B:C1 name eth1
What if you also want to know the name of the device, as well
as the interface on the device? This query won't give you that
information, because you have limited the search to the interface
node in the FROM clause. To include the name of the
device on which each interface resides, see
Example 5.
Example 5: Limiting searches at the right node
To get any information about the device, such as its name, you must select from the device node, not from the interface node. In other words, you need to include a path-scoped projection like the one used in Example 1:
SELECT interface/(mac_address, name), name FROM /network/device
When run against the sample database, this query returns correlated results:
row
interface/(mac_address, name)
item
mac_address 01:01:02:03:04:05
name eth0
name null
row
interface/(mac_address, name)
item
mac_address 02:A1:A2:A3:A4:A4
name eth0
item
mac_address 03:A1:A2:A3:A4:A5
name eth1
name null
row
interface/(mac_address, name)
item
mac_address 04:A1:A2:A3:A4:A8
name eth0
item
mac_address 05:A1:A2:A3:A4:A9
name eth1
name null
row
interface/(mac_address, name)
item
mac_address 06:13:72:F3:0A:F5
name eth0
item
mac_address 07:13:72:F3:0A:F6
name eth1
name null
row
interface/(mac_address, name)
item
mac_address 08:16:CB:FF:FE:66
name eth0
item
mac_address 09:16:CB:FF:FE:67
name eth1
item
mac_address 10:16:CB:FF:FE:68
name eth2
item
mac_address 11:16:CB:FF:FE:69
name eth3
name null
row
interface/(mac_address, name)
item
mac_address 12:10:D8:99:2B:C2
name eth0
item
mac_address 13:10:D8:99:2B:C1
name eth1
name null
Example 6: Abbreviating the projected path
This query uses .. to abbreviate the projected path. The query
extracts information about environment variables on systems for which
GoToManage has WMI information, which can be useful in understanding how running
processes behave.
SELECT ../win32_operatingsystem/csname as "System",
name as "Environment Variable Name",
variablevalue as "Environment Variable Value"
FROM /network/device/wmi/win32_environment
ORDER BY 1
Depending on the database, this query fetches information about names and dynamic values such as PATH, TEMP, WINDIR, and so on, and displays the correlated results in ascending order by system name, similar to this:
row System JAKARTA Environment Variable Name TMP Environment Variable Value %USERPROFILE%\Local Settings row System KATHMANDU Environment Variable Name ComSpec Environment Variable Value %SystemRoot%\system32\cmd.exe row System LISBON Environment Variable Name Path Environment Variable Value %SystemRoot%\system32 etsnmp\bin row System MILAN Environment Variable Name windir Environment Variable Value %SystemRoot% row System TAIPEI Environment Variable Name FP_NO_HOST_CHECK Environment Variable Value NO . . .
