fix(ENGKNOW-3933): MAP/MULTIMAP cache key, single load per request and lower memory

[gmagnu]

Summary

Changes to MapAndListUtilities (the loaders behind MAP, MULTIMAP and INSET):

1. Cache-key bug (correctness). The per-request cache key was built as "map"+filename+ic+oc.mkString(",")+asSet (and the same without asSet for multimap).
   • It left out caseInsensitive, so MAP -cis and a plain MAP of the same file in one request shared one cached map, and one of them returned wrong results.
   • It had no separator between ic and oc, so ic=1, oc=[23] and ic=12, oc=[3] collided.
   • The key is now delimited and includes every parameter.
2. Single load per request. Concurrent pipelines of a request share the session cache (for example pgor partitions), and each one missed the cache and built its own full copy of the map. Loads now happen under a per-(request, key) lock that re-checks the cache after it is acquired. The lock entry is removed afterwards.
3. Value dedup. Equal value strings share one instance while a map loads. MAP value columns repeat heavily. The pool is capped at 100k distinct values, so maps with mostly unique values don't pay for a large pool.
4. MULTIMAP peak. Entries are moved into a presized output map instead of copied, so the ListBuffer map and the Array map are never both fully held.

Measurements

Heap retained after GC. Synthetic 1M-line files with values drawn from 50 distinct strings.

	before	after
Single map, 1M keys	160.8 MB	98.4 MB (−39%)
Multimap, 200k keys × 5 values, retained	90.4 MB	28.0 MB (−69%)
Multimap, peak during load	350.1 MB	305.9 MB (−13%)

Tests

• New UTestMapAndListUtilities, 6 tests. All 6 fail on main and pass with this change:
  • -cis vs plain map and multimap caching
  • the ic/oc key collision
  • concurrent loads reading the file once: main read it 4,000 times with 4 threads instead of 1,000
  • value string sharing for map and multimap, with multimap value order kept
• Existing map tests pass: UTestGorMapMultimap, UTestMapLookup, UTestMultiMapLookup, UTestGorPipeSession, UTestDAGMapAnalysis (42 tests, including the new ones).
• :model:test passes: 1,548 tests, 17 skipped.

🤖 Generated with Claude Code

[github-actions]

Junit Tests - Summary

4 859 tests  +8   4 688 ✅ +9   20m 2s ⏱️ - 1m 10s
  506 suites +1     171 💤  - 1 
  506 files   +1       0 ❌ ±0 

Results for commit c9c1467. ± Comparison against base commit 9536c2f.