itxiangkui created CALCITE-5187:
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Summary: "CalciteSchema call getSubSchemaMap when prepareSql" will
Causes SQL execution to slow down
Key: CALCITE-5187
URL: https://issues.apache.org/jira/browse/CALCITE-5187
Project: Calcite
Issue Type: Improvement
Reporter: itxiangkui
Attachments: Screenshot from 2022-06-10 11-17-02.png, Screenshot from
2022-06-10 11-18-54.png
# We define the structure of Schema-Tree: catalog->database->table
# 2. A time series database is designed. Schema information is stored in the
traditional Mysql database. Therefore, methods such as
Schema.getSubSchemaNames() Schema.getSubSchemaMap() will be frequently called
when executing SQL, especially in the validate phase.
# Query a SQL sample as follows:
select * from `catalog`.`database`.`xxtable` limit 10
# Modified part of the code and connected to the opentracing system (jaeger)
# DEBUG tracks and analyzes the entire execution process of SQL to analyze why
it is slow, so as to optimize our system
Here is one of our SQL executions:
!Screenshot from 2022-06-10 11-18-54.png!
Apparently, ICUserCatalogSchema.getSubSchemaMap() is called many times and it
increases with the number of databases
The debug code finds that the prepareSql stage will call the gatherLattices
method, and gatherLattices will access all Schema information, which
corresponds to databases
{code:java}
private static void gatherLattices(CalciteSchema schema,
List<CalciteSchema.LatticeEntry> list) {
list.addAll(schema.getLatticeMap().values());
for (CalciteSchema subSchema : schema.getSubSchemaMap().values()) {
gatherLattices(subSchema, list);
}
} {code}
My question is, why do you care about other database information when querying
a table, and are there any suggestions for improvement here...
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