Add selective index updates (n/m) to the heap table AM

.clangd

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+Diagnostics:
+  MissingIncludes: None
+InlayHints:
+  Enabled: true
+  ParameterNames: true
+  DeducedTypes: true
+CompileFlags:
+  CompilationDatabase: build/       # Search build/ directory for compile_commands.json
+  Remove: [ -Werror ]
+  Add:
+  - -DDEBUG
+  - -DLOCAL
+  - -DPGDLLIMPORT=
+  - -DPIC
+  - -O2
+  - -Wall
+  - -Wcast-function-type
+  - -Wconversion
+  - -Wdeclaration-after-statement
+  - -Wendif-labels
+  - -Werror=vla
+  - -Wextra
+  - -Wfloat-equal
+  - -Wformat-security
+  - -Wimplicit-fallthrough=3
+  - -Wmissing-format-attribute
+  - -Wmissing-prototypes
+  - -Wno-format-truncation
+  - -Wno-sign-conversion
+  - -Wno-stringop-truncation
+  - -Wno-unused-const-variable
+  - -Wpointer-arith
+  - -Wshadow
+  - -Wshadow=compatible-local
+  - -fPIC
+  - -fexcess-precision=standard
+  - -fno-strict-aliasing
+  - -fvisibility=hidden
+  - -fwrapv
+  - -g
+  - -std=c11
+  - -I.
+  - -I../../../../src/include

.envrc

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+watch_file flake.nix
+use flake
+
+# libumem: pass -DUSE_LIBUMEM to enable palloc integration at compile time
+export CFLAGS="${CFLAGS:+$CFLAGS }-DUSE_LIBUMEM"
+
+# libumem: uncomment to enable malloc replacement via LD_PRELOAD
+#export LD_PRELOAD="$LIBUMEM_HOME/lib/libumem.so"
+
+# UMEM_DEBUG controls debug features:
+#   default       - audit+contents+guards (comprehensive)
+#   audit[=N]     - allocation auditing, optional stack frames
+#   guards        - redzone + deadbeef (detect overruns/use-after-free)
+#   verbose       - error messages to stderr
+#   firewall=N    - guard pages for objects >= N bytes
+#   nosignal      - abort if called from signal handler
+#   checknull     - abort if allocation returns NULL
+#export UMEM_DEBUG="default"
+#export UMEM_DEBUG="audit=10,guards"
+#export UMEM_DEBUG="guards,verbose"
+export UMEM_DEBUG="audit=10,guards,checknull,nosignal"
+
+# UMEM_OPTIONS controls allocator behavior:
+#   backend=sbrk|mmap         - memory backend
+#   allocator=best|first|next - allocation strategy
+#   perthread_cache=SIZE      - per-thread cache (e.g. 2m)
+#   nomagazines               - disable caching (simplifies debugging)
+#   concurrency=N             - max CPUs
+#   numa=1                    - NUMA-aware allocation
+#export UMEM_OPTIONS="backend=mmap"
+#export UMEM_OPTIONS="nomagazines"
+export UMEM_OPTIONS="backend=mmap"
+
+# UMEM_LOGGING controls logging:
+#   transaction[=SIZE]  - audit log (default 64k)
+#   contents[=SIZE]     - freed object contents (default 256 bytes)
+#   fail[=SIZE]         - failed allocations
+#export UMEM_LOGGING="transaction=1m,fail=64k"
+export UMEM_LOGGING="transaction=1m,fail=64k"

.gdbinit

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+# HOT Indexed Updates — GDB breakpoints for code review
+#
+# Usage:  gdb -x .gdbinit <postgres-binary>
+# Or from gdb:  source .gdbinit
+#
+# These breakpoints cover the major code paths introduced or modified by
+# the HOT indexed updates patch series.  They are organized by subsystem
+# to make it easy to enable/disable groups during debugging.
+#
+# Tip: to skip to a specific subsystem, disable all then enable selectively:
+#   disable breakpoints
+#   enable 1 2 3          # just the update-decision group
+
+# =========================================================================
+# 1. UPDATE DECISION — heap_update() HOT/HOT-indexed/non-HOT choice
+#    src/backend/access/heap/heapam.c
+# =========================================================================
+
+# Main entry: heap_update
+break heapam.c:3210
+
+# HOT decision block: pure HOT vs HOT indexed vs non-HOT
+# Line 4019: pure HOT (no indexed columns changed)
+# Line 4024: HOT indexed path (non-catalog, some indexed columns changed)
+# Line 4031: predict augmented tuple size
+# Line 4033: size+space check before creating augmented tuple
+break heapam.c:4019
+break heapam.c:4024
+break heapam.c:4033
+
+# Set HEAP_INDEXED_UPDATED flag on new tuple before page insertion
+break heapam.c:4101
+
+# Restore HEAP_INDEXED_UPDATED on old tuple (only if it previously had it)
+break heapam.c:4147
+
+# =========================================================================
+# 2. TUPLE CREATION — building the augmented tuple with embedded bitmap
+#    src/backend/access/heap/heapam.c
+# =========================================================================
+
+# Predict augmented tuple size (returns 0 if t_hoff would overflow)
+break heap_hot_indexed_tuple_size
+
+# Create augmented tuple with embedded modified-column bitmap
+break heap_hot_indexed_create_tuple
+
+# Serialize Bitmapset into raw bytes in tuple header
+break heap_hot_indexed_serialize_bitmap
+
+# =========================================================================
+# 3. BITMAP UTILITIES — raw bitmap operations for chain following
+#    src/backend/access/heap/heapam.c
+# =========================================================================
+
+# Compute raw bitmap byte size from natts
+break heap_hot_indexed_bitmap_raw_size
+
+# Check if tuple header has room for bitmap between null bitmap and data
+break heap_hot_indexed_has_bitmap_space
+
+# Read HOT indexed bitmap from tuple header (returns Bitmapset)
+break heap_hot_indexed_read_bitmap
+
+# Fast overlap check: does tuple's raw bitmap overlap with indexed_attrs?
+break heap_hot_indexed_bitmap_overlaps_raw
+
+# OR a tuple's raw bitmap into an accumulator buffer
+break heap_hot_indexed_bitmap_or_raw
+
+# Check if accumulated raw bitmap overlaps with indexed_attrs
+break heap_hot_indexed_accum_overlaps
+
+# Merge bitmaps from dead tuples into a target tuple on the page
+break heap_hot_indexed_merge_bitmaps_raw
+
+# Deserialize raw bytes back to Bitmapset
+break heap_hot_indexed_deserialize_bitmap
+
+# =========================================================================
+# 4. INDEX SCAN — HOT chain following with stale-entry detection
+#    src/backend/access/heap/heapam_indexscan.c
+# =========================================================================
+
+# Main HOT chain search with indexed update awareness
+break heap_hot_search_buffer
+
+# Redirect-with-data: initialize bitmap accumulator from collapsed redirect
+break heapam_indexscan.c:182
+
+# Accumulate bitmap from INDEXED_UPDATED tuple in chain
+break heapam_indexscan.c:250
+
+# Stale entry detection: accumulated bitmap overlaps this index's attrs
+break heapam_indexscan.c:297
+
+# =========================================================================
+# 5. INDEX SCAN SETUP — indexed_attrs bitmap computation
+#    src/backend/access/index/indexam.c
+# =========================================================================
+
+# Compute indexed_attrs for HOT indexed update chain following
+break indexam.c:299
+
+# =========================================================================
+# 6. INDEX INSERTION — skip unchanged indexes for HOT indexed updates
+#    src/backend/executor/execIndexing.c
+# =========================================================================
+
+# Entry: insert/update index tuples
+break ExecInsertIndexTuples
+
+# Index skip decision: skip indexes whose attrs don't overlap modified set
+break execIndexing.c:370
+
+# =========================================================================
+# 7. PRUNING — chain collapsing and redirect-with-data
+#    src/backend/access/heap/pruneheap.c
+# =========================================================================
+
+# Main prune function
+break heap_page_prune_and_freeze
+
+# Per-chain pruning entry
+break heap_prune_chain
+
+# Chain collapsing: collect bitmaps from dead INDEXED_UPDATED intermediates
+break pruneheap.c:1802
+
+# OR dead tuple bitmaps into combined bitmap
+break pruneheap.c:1836
+
+# Record redirect-with-data for execute phase
+break pruneheap.c:1863
+
+# Execute phase: apply redirect-with-data entries on the page
+break pruneheap.c:1287
+
+# =========================================================================
+# 8. WAL REPLAY — recovery of HOT indexed updates
+#    src/backend/access/heap/heapam_xlog.c
+# =========================================================================
+
+# WAL replay for XLOG_HEAP2_INDEXED_UPDATE
+break heap_xlog_indexed_update
+
+# =========================================================================
+# 9. WAL LOGGING — writing HOT indexed update records
+#    src/backend/access/heap/heapam.c
+# =========================================================================
+
+# WAL logging for heap updates (handles indexed_update flag)
+break log_heap_update
+
+# Serialize redirect-with-data into WAL record (pruneheap.c)
+break pruneheap.c:2936

.github/.gitignore

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+# Node modules
+scripts/ai-review/node_modules/
+# Note: package-lock.json should be committed for reproducible CI/CD builds
+
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+scripts/ai-review/cost-log-*.json
+scripts/ai-review/*.log
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+*.swp
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+*~
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