perf(core): optimize parseInt/parseLong hot paths in Numbers.java

[misrasaurabh1]

Summary

Optimize the inner loops of parseInt0 and parseLong0 in Numbers.java to reduce branch overhead on the digit path, which is taken on every character of a valid number string.

Both functions are called from 334 sites across the codebase (265 parseInt, 69 parseLong), making them a recurring cost in SQL parsing, CSV import, ILP ingestion, and config loading.

Changes

parseInt0 — reorder if-else-if so the digit range check comes first.

Before:

if (c == '_') { ... }           // checked first, rarely true
else if (c < '0' || c > '9') { ... }
else { /* digit — hot path */ }

After:

if (c >= '0' && c <= '9') { /* digit — hot path */ }
else if (c == '_') { ... }
else { throw; }

For a digit, this reduces 3 comparisons to 2 per loop iteration.

parseLong0 — replace the switch (c | 32) loop with an if-else-if chain, putting the digit check first.

Before:

switch (c | 32) {          // bitwise OR applied to every character
    case 'l':  ...
    case 127:  ...          // '_' after OR
    default:
        if (c < '0' || c > '9') throw;
        /* digit */
}

After:

if (c >= '0' && c <= '9') { /* digit */ }
else if (c == '_') { ... }
else if (c == 'l' || c == 'L') { ... }   // no OR needed
else { throw; }

For a digit, this reduces 5 operations (1 OR + 2 switch comparisons + 2 range checks) to 2 comparisons.

The L-suffix validity check is also tightened from i == 0 (incorrect for non-zero start offsets) to digitCounter == 0, which correctly rejects 'L' appearing before any digits regardless of starting position.

Evidence

Informal micro-benchmark (10M iterations, 1000 varied random inputs, JVM warmed):

Operation	Before	After	Delta
parseLong 10-digit	22.3 ns/op	19.8 ns/op	-11%
parseLong 3-digit	12.0 ns/op	9.3 ns/op	-22%
parseInt 9-digit	20.7 ns/op	19.0 ns/op	-8%

Benchmark method: 10M iterations over 1000 varied random strings, JVM warmed with 200K iterations first.

Test plan

• NumbersTest — 195 tests, all pass
• SqlLexerTest, SqlParserTest — 1000 tests, all pass
• CastTest, FunctionParserTest — 522 tests, all pass