Istvan Toth created PHOENIX-6916:
------------------------------------
Summary: Degenerate scan generated for timestamp with desc global
index
Key: PHOENIX-6916
URL: https://issues.apache.org/jira/browse/PHOENIX-6916
Project: Phoenix
Issue Type: Bug
Reporter: Istvan Toth
For some non-empty timestamp ranges, Phoenix generates a query plan with a
degenerate scan if DESC index is created on the timestamp field:
{noformat}
create table data (id varchar primary key, ts timestamp);
create index data_idx on data(ts desc);
0: jdbc:phoenix:> explain select id, ts from data where ts >= TIMESTAMP
'2023-02-23 13:30:00' and ts < TIMESTAMP '2023-02-23 13:40:00';
+-------------------------------+----------------+---------------+-------------+
| PLAN | EST_BYTES_READ | EST_ROWS_READ | EST_INFO_TS |
+-------------------------------+----------------+---------------+-------------+
| DEGENERATE SCAN OVER DATA_IDX | null | null | null |
+-------------------------------+----------------+---------------+-------------+
1 row selected (0.012 seconds)
0: jdbc:phoenix:> explain select id, ts from data where ts >= TIMESTAMP
'2023-02-23 13:30:00' and ts < TIMESTAMP '2023-02-23 13:50:00';
+----------------------------------------------------------------------------------------------------------------+----------------+---------------+-------------+
| PLAN
| EST_BYTES_READ | EST_ROWS_READ | EST_INFO_TS
|
+----------------------------------------------------------------------------------------------------------------+----------------+---------------+-------------+
| CLIENT 1-CHUNK PARALLEL 1-WAY ROUND ROBIN RANGE SCAN OVER DATA_IDX
[~1,677,160,200,000] - [~1,677,159,000,000] | null | null |
null |
| SERVER FILTER BY FIRST KEY ONLY
| null | null | null
|
+----------------------------------------------------------------------------------------------------------------+----------------+---------------+-------------+
2 rows selected (0.009 seconds)
0: jdbc:phoenix:localhost:59231> explain select /*+NO_INDEX*/ id, ts from data
where ts >= TIMESTAMP '2023-02-23 13:30:00' and ts < TIMESTAMP '2023-02-23
13:40:00';
+---------------------------------------------------------------------------------------------------------------+----------------+---------------+-------------+
| PLAN
| EST_BYTES_READ | EST_ROWS_READ | EST_INFO_TS |
+---------------------------------------------------------------------------------------------------------------+----------------+---------------+-------------+
| CLIENT 1-CHUNK PARALLEL 1-WAY ROUND ROBIN FULL SCAN OVER DATA
| null | null | null |
| SERVER FILTER BY (TS >= TIMESTAMP '2023-02-23 13:30:00.000' AND TS <
TIMESTAMP '2023-02-23 13:40:00.000') | null | null | null
|
+---------------------------------------------------------------------------------------------------------------+----------------+---------------+-------------+
{noformat}
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