ccoffline opened a new issue #4581:
URL: https://github.com/apache/incubator-doris/issues/4581
**Describe the bug**
When using select condition like "-1=-1" may cause SelectNode.cardinality
computing error.
`// at org.apache.doris.planner.SelectNode.computeStats(SelectNode.java:70)`
`cardinality = Math.round(((double) getChild(0).cardinality) *
computeSelectivity());`
`Preconditions.checkState(cardinality >= 0);`
This cardinality may be less than 0.
**To Reproduce**
Steps to reproduce the behavior:
1. Create a table
> CREATE TABLE \`table1\` (
\`city_id\` bigint(20) NULL,
\`tag_id\` bigint(20) NULL,
\`dt\` bigint(20) NULL,
\`num\` bigint(20) NULL
) ENGINE=OLAP
DUPLICATE KEY(\`city_id\`, \`tag_id\`, \`dt\`)
COMMENT "OLAP"
PARTITION BY RANGE(\`dt\`)
(PARTITION p20200102 VALUES [("20200101"), ("20200102")),
PARTITION p20200103 VALUES [("20200102"), ("20200103")))
DISTRIBUTED BY HASH(\`city_id\`) BUCKETS 5
PROPERTIES (
"replication_num" = "1",
"in_memory" = "false",
"storage_format" = "DEFAULT"
);
You may need to insert some data and wait for the "cardinality" to be > 0 (I
still dont know how the "cardinality" works).
> INSERT INTO table1 VALUES (1, 2, 20200102, 3);
2. Launch a query
> SELECT rank, tag_id
FROM (
SELECT row_number() OVER (ORDER BY num DESC) AS rank, tag_id
FROM table1
) t
WHERE -1=-1 or tag_id in (-1)
LIMIT 10
;
When the table is not empty (maybe), the cardinality will be > 0,
`computeSelectivity()` < 0, then the error occur.
I tried to reduce some elements and this is the minimum sql to reproduce the
bug.
Could someone explain what does the cardinality and selectivity means? Is
`Preconditions.checkState(cardinality >= 0);` neccessary?
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