Fold PhysicalColumnIndexContainer's IndexTypeMap into a presence mask and a dense reader array

[xiangfu0]

What

PhysicalColumnIndexContainer stored its readers in an IndexTypeMap holding a span-sized IndexReader[]: with forward index at numeric id 2 and null vector at 8, a column with two readers allocated seven slots. It now keeps a long presence mask plus a densely packed, exactly sized reader array, so getIndex is a shift, mask and Long.bitCount instead of a range check, at the same O(1) cost. Construction also drops the transient per-column ArrayLists.

A Preconditions.checkState rejects a numeric index id of 64 or above at construction rather than silently misbehaving; OSS uses 13 ids today.

Tests

PhysicalColumnIndexContainerTest: forward only, forward plus null vector, and a mix spanning the lowest and a high id, asserting getIndex returns the created reader for present types and null for absent ones, that forwardIndexOnly filtering still applies, and that close closes each reader exactly once.

Why

A server keeps one metadata object graph per (segment, column) for as long as the segment is loaded, so on wide tables the per-column footprint decides how many segments a server can hold. Measured end to end on a 1000-column segment, this series takes the heap retained at load from 4.08 MB to 0.175 MB per segment (4,080 to 174 bytes per column), with a fully compacting collector on both sides. No on-disk format change, the /tables/{table}/segments/{segment}/metadata JSON stays byte-identical, and every public and SPI signature keeps working.

Stack

Based on #19474. Review this PR against its base for this layer's changes.

Current open chain; #19480 (lazy index-size storage) is already merged, and #19476 is absorbed into #19473.

1. Share FieldSpecs and repeated values across segment metadata loads #19473 shared FieldSpecs, canonical default-null values, and interned strings
2. Delegate immutable DataSourceMetadata to ColumnMetadata instead of snapshotting it #19474 delegating immutable DataSourceMetadata
3. Fold PhysicalColumnIndexContainer's IndexTypeMap into a presence mask and a dense reader array #19475 presence-mask index container
4. Materialize immutable-segment columns lazily behind an opt-in instance config (default off) #19477 opt-in lazy column materialization
5. Slim ColumnMetadataImpl to 72 bytes and derive the per-segment Schema lazily #19478 slim ColumnMetadataImpl and lazy per-segment Schema
6. Store numeric column min/max as primitives instead of boxed Comparables #19479 primitive numeric min/max
7. Hold segment column metadata in sorted arrays and derive the map on demand #19481 sorted-array column metadata storage
8. Stop the segment preprocess from building a Schema per segment #19486 segment preprocessing without building a Schema
9. Prune segments from column metadata instead of materializing them #19511 segment pruning directly from column metadata

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.93939% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.75%. Comparing base (caac249) to head (e068c8a).

Files with missing lines	Patch %	Lines
...ent/index/column/PhysicalColumnIndexContainer.java	93.93%	2 Missing ⚠️

Additional details and impacted files

@@                              Coverage Diff                              @@
##             xiangfu0/data-3221-3-datasource-adapter   #19475      +/-   ##
=============================================================================
+ Coverage                                      67.71%   67.75%   +0.03%     
  Complexity                                      1450     1450              
=============================================================================
  Files                                           3490     3490              
  Lines                                         225025   225009      -16     
  Branches                                       35529    35527       -2     
=============================================================================
+ Hits                                          152384   152452      +68     
+ Misses                                         60614    60528      -86     
- Partials                                       12027    12029       +2     

Flag	Coverage Δ
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-25	67.75% <93.93%> (+0.03%)	⬆️
lane-a	100.00% <ø> (ø)
lane-b	0.00% <ø> (ø)
temurin	67.75% <93.93%> (+0.03%)	⬆️
unittests	67.75% <93.93%> (+0.03%)	⬆️
unittests1	57.83% <72.72%> (+0.01%)	⬆️
unittests2	39.51% <93.93%> (+0.01%)	⬆️

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