Show Tag Keys Problem with Given Retention Policy

[lvheyang]

Bug report

System info: [InfluxDB 0.12.2, Mac OS X 10.11.4]

Steps to reproduce:

# create database 
curl -G http://localhost:8086/query --data-urlencode "q=CREATE DATABASE mydb"

# create retention policy * 2 (myrp1, myrp2),  set myrp2 as DEFAULT retention policy
curl -G http://localhost:8086/query --data-urlencode "q=CREATE RETENTION POLICY myrp1 ON mydb DURATION 365d REPLICATION 1 DEFAULT"
curl -G http://localhost:8086/query --data-urlencode "q=CREATE RETENTION POLICY myrp2 ON mydb DURATION 365d REPLICATION 1 DEFAULT"

# insert points into myrp1.cpu
curl -i -XPOST 'http://localhost:8086/write?db=mydb&rp=myrp1' --data-binary 'cpu,host=server01,region=us-west value=0.64'

Expected behavior and Actual behavior

# show tag keys of measurement cpu
curl -G http://localhost:8086/query\?db\=mydb --data-urlencode "q=show tag keys from cpu"

expected: {"results":[{}]}
got: {"results":[{}]}

# show tag keys of measurement cpu in myrp2 
curl -G http://localhost:8086/query\?db\=mydb --data-urlencode "q=show tag keys from mydb.myrp2.cpu"

expected: {"results":[{}]}
got: {"results":[{}]}

# show tag keys of measurement cpu in myrp1
curl -G http://localhost:8086/query\?db\=mydb --data-urlencode "q=show tag keys from mydb.myrp1.cpu"

expected: {"results":[{"series":[{"name":"cpu","columns":["tagKey"],"values":[["host"],["region"]]}]}]}
got: {"results":[{}]}

Additional info:

• Query Log: All of the statements were rewrite to SELECT tagKey FROM mydb.myrp2._tagKeys WHERE _name = 'cpu'. It rewrite every source into default retention policy.

[query] 2016/04/27 20:18:22 SELECT tagKey FROM mydb.myrp2._tagKeys WHERE _name = 'cpu'
[httpd]2016/04/27 20:18:22 ::1 - - [27/Apr/2016:20:18:22 +0800] GET /query?db=mydb&q=show+tag+keys+from+mydb.myrp1.cpu HTTP/1.1 200 16 - curl/7.43.0 223a4a69-0c72-11e6-8008-000000000000 542.083µs
[query] 2016/04/27 20:18:28 SELECT tagKey FROM mydb.myrp2._tagKeys WHERE _name = 'cpu'
[httpd]2016/04/27 20:18:28 ::1 - - [27/Apr/2016:20:18:28 +0800] GET /query?db=mydb&q=show+tag+keys+from+mydb.myrp2.cpu HTTP/1.1 200 16 - curl/7.43.0 25ddf2af-0c72-11e6-8009-000000000000 378.017µs
[query] 2016/04/27 20:18:33 SELECT tagKey FROM mydb.myrp2._tagKeys WHERE _name = 'cpu'
[httpd]2016/04/27 20:18:33 ::1 - - [27/Apr/2016:20:18:33 +0800] GET /query?db=mydb&q=show+tag+keys+from+cpu HTTP/1.1 200 16 - curl/7.43.0 28d8e93c-0c72-11e6-800a-000000000000 630.81µs

• The possible problem position in source code (in influxql/statement_rewriter.go line 157). I noticed that the previous statement's database & retention policy was discarded. But I don't know why? Are there any other considerations?

func rewriteShowTagKeysStatement(stmt *ShowTagKeysStatement) (Statement, error) {
    // Check for time in WHERE clause (not supported).
    if HasTimeExpr(stmt.Condition) {
        return nil, errors.New("SHOW TAG KEYS doesn't support time in WHERE clause")
    }

    return &SelectStatement{
        Fields: []*Field{
            {Expr: &VarRef{Val: "tagKey"}},
        },
        Sources: []Source{
            &Measurement{Name: "_tagKeys"},  // why not use previous statement's db and rp
        },
        Condition:  rewriteSourcesCondition(stmt.Sources, stmt.Condition),
        Offset:     stmt.Offset,
        Limit:      stmt.Limit,
        SortFields: stmt.SortFields,
        OmitTime:   true,
        Dedupe:     true,
    }, nil
}

thx

[lvheyang]

I try to fix it. related pr #6481

[lvheyang]

merged & closed
thx