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Grant Henke updated KUDU-2731: ------------------------------ Component/s: perf > Getting column schema information from KuduSchema requires copying a > KuduColumnSchema object > -------------------------------------------------------------------------------------------- > > Key: KUDU-2731 > URL: https://issues.apache.org/jira/browse/KUDU-2731 > Project: Kudu > Issue Type: Improvement > Components: perf > Affects Versions: 1.9.0 > Reporter: William Berkeley > Priority: Major > > I'm looking at a CPU profile of Impala inserting into Kudu. > {{KuduTableSink::Send}} has code that schematically does the following: > {noformat} > for each row in the batch > for each column > if (schema.Column(col_idx).isNullable()) { > write->mutable_row()->SetNull(col); > } > } > } > {noformat} > See > [kudu-table-sink.cc|https://github.com/apache/impala/blob/branch-3.1.0/be/src/exec/kudu-table-sink.cc#L236]. > However, {{KuduSchema::Column}} copies the column schema and returns it by > value, so the if statement constructs and destroys a column schema object > just to check if the column is nullable. > This is by far the biggest user of CPU in the Impala process (35% or so). The > workload might be I/O bound writing to Kudu anyway, though. Nevertheless, we > should provide a way to avoid this copying in the API, either by adding a > method like > {noformat} > class KuduSchema { > const KuduColumnSchema& get_column(int idx); > } > {noformat} > or a method like > {noformat} > class KuduSchema { > bool is_column_nullable(int idx); > } > {noformat} > The former is the most flexible while the latter frees the client from > worrying about holding the ref longer than the KuduColumnSchema object lives. > We might need to add a number of methods similar to the latter method to > cover other potentially useful things like checking encoding, type, etc. -- This message was sent by Atlassian Jira (v8.3.4#803005)