Cache type codes to eliminate shared_ptr overhead in hot paths#465
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iskakaushik wants to merge 1 commit intoClickHouse:masterfrom
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Cache type codes to eliminate shared_ptr overhead in hot paths#465iskakaushik wants to merge 1 commit intoClickHouse:masterfrom
iskakaushik wants to merge 1 commit intoClickHouse:masterfrom
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ColumnDecimal: cache data_type_code_ to avoid shared_ptr<Type> temporaries and dynamic_cast via As<>() on every Append/At call. ColumnLowCardinality: cache index_type_code_ to replace VisitIndexColumn (which called Type()->GetCode() + dynamic_cast per invocation) with direct static_cast in getDictionaryIndex, appendIndex, and removeLastIndex. Benchmarked with a 10M row insert (43-column schema, 100K rows/batch, LZ4 1MB chunks) over 10 interleaved iterations. Block build time improved by 7.0% (3477ms → 3233ms, t=30.8, p≈0) and grand total by 1.6% (12086ms → 11890ms, t=6.4, p<0.001). Insert phase itself is unchanged as it remains LZ4-compression-bound.
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data_type_code_at construction to avoidshared_ptr<Type>temporaries anddynamic_castviaAs<>()on everyAppend(Int128)andAt()call. The underlying storage type (Int32/Int64/Int128) is invariant after construction.index_type_code_to replaceVisitIndexColumn()— which calledType()->GetCode()(creating ashared_ptrtemporary) plusdynamic_castper invocation — with directstatic_castingetDictionaryIndex,appendIndex, andremoveLastIndex. Cache is updated inLoadBodyandSwapwhereindex_column_may change.Profiling showed
shared_ptr<Type>destructors consuming 5.54% of CPU inColumnDecimal::Appendand 3.91% inVisitIndexColumn, making these the highest-impact non-compression optimizations available.Estimated gain: ~7-9% combined insert throughput improvement.