[collectd] wip patch to annotate postgres plugin values

[Mark Wong]

Hi all,

I have a couple patches put together for annotating postgresql plugin 
values with database, schema, table, and index names.  I'm not sure I 
did this in the best way because I copied several udb_* functions into 
postgresql.c with primarily parameter changes in order to pass extra 
data around.  Any suggestions for these 2 changes:

https://github.com/mwongatemma/collectd/commit/2ac90b916aacfe9d992e399b33ac76918e54c33d
https://github.com/mwongatemma/collectd/commit/d7ece276cd9c9a03a9a50fe2be67c4469dc8a478

To illustrate what I was attempting to accomplish:

SELECT datname, numbackends
FROM pg_stat_database

This query lets us get stats for all databases in a single query.  In
the <Database> tag the following parameter needs to be set to annotate
the data with which database the data is from:

DatabasenameColumn 0


Similarly for table stats:

SELECT schemaname, relname, seq_scan
FROM pg_stat_all_tables

To keep the data distinct, the following parameters need to be set for
each value selected in the <Result> tag, resulting in a reversed order
naming scheme in type_instance:

InstancePrefix "seq_scan"
InstancesFrom "relname" "schemaname"

In the <Database> tag the following parameters need be set to annotate
the data with the schema and table information:

SchemanameColumn 0
TablenameColumn 1


Again for index stats:

SELECT schemaname, relname, indexrelname, idx_scan
FROM pg_stat_all_indexes

To keep the data distinct, the following parameters need to be set for
each value selected in the <Result> tag, resulting in a reversed order
naming scheme in type_instance:

InstancePrefix "idx_scan"
InstancesFrom "indexrelname" "relname" "schemaname"

In the <Database> tag the following parameters need be set to annotate
the data with the schema, table, and index information:

SchemanameColumn 0
TablenameColumn 1
IndexnameColumn 2

How does that sound?

Regards,
Mark

-- 
Mark Wong
Developer | Emma(R)
mark.wong at myemma.com
800.595.4401

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