perf: optimize std.map, std.flatMap, and std.filterMap allocations#670
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stephenamar-db merged 1 commit intodatabricks:masterfrom Apr 8, 2026
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Three stdlib array function optimizations: 1. std.map: Replace .map(closure) with pre-sized array + while-loop. Eliminates closure allocation and intermediate array creation. 2. std.flatMap: Two-pass approach for array variant: - First pass: apply function, collect sub-arrays, count total length - Second pass: System.arraycopy into pre-sized result array Avoids .flatMap's intermediate ArrayBuilder resizing. 3. std.filterMap: Replace .flatMap + Option boxing with while-loop and ArrayBuilder. Eliminates Some/None wrapping per element. Upstream: jit branch commit 9cb95af Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
stephenamar-db
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Apr 8, 2026
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Motivation
std.map,std.flatMap, andstd.filterMapallocate intermediate collections (iterators, builders) for each call. These stdlib functions are among the most frequently called operations in Jsonnet programs.Key Design Decision
Replace functional collection operations with direct array-based loops:
Modification
ArrayModule.scala: Optimizedstd.map,std.flatMap,std.filterMapwith direct array operationsBenchmark Results
JMH (JVM, 3 iterations)
Analysis
References
he-pin/sjsonnetjit branch stdlib optimizationResult
-12% to -18% JVM improvement by eliminating intermediate collections in map/flatMap/filterMap.