Eliminate blockmap (#318)

* wip reset

* Use lantern_slot_t for lantern usage

* Update WAL version and validate_index strategy to new neighbor length

* Fix test regressions caused by neighbor id length change

* Rename lantern_slot_t to ldb_lantern_slot_union_t

* Move to using an anonymous namespace in usearch_storage.cpp

* Pass an item_pointers array to populate rewrite info during index build

* Add API to interface with usearch node neighbors

* Implement node neighbor rewriting logic (rewriting disabled for now)

* Use 64bit ID for node retriever

* Update entry_slot after updating all graph neighbors. (last step for converting built index into new blockmap-less format)

* WIP: fix all retrievers to assume itemPointerData neighbors

* Fix remaining version handling info for scans

* Rename HnswIndexTuple id to seqid

* Pass slot externally to make inserts work

* Add slot type scalar kind in usearch

* remove blockmap test

* Delete some of blockmap handling

* Update regression tests assuming there is no blockmap in index structure

* Delete a lot of the blockmap code

* Remove continue_blockmap_initialization SQL interface

* Add update test to 0.3.0

* Delete more unused code

* Do not copy blockmap to scan retriever cache

* Disable validate_index

* Simplify node retrievers

* Add usearch performance patches

* Add perf installation instructions (tested on gcp)

* Update binary file tests to the new format

* in cmakefiles Add option to avoid omiting frame pointer and get rid of robin-map includes

* Update Dockerfile.dev with postgres GUCs

- set wal_level to logical
- set shared_buffers
- set listen_addresses to '*' so host can connect

* Remove blockmap-related and failure-points tests

* Add level distribution snippet

* Remove remnants of backward compatible upgrade support

* Add a note on handling of pq pages in deletes and WAL rewriting

* Remove extra lines from update script

* update usearch

* remove failure point test

* disable failure points by default

* update usearch (uint48 hasher to work for index creation from pg)

* Use unsigned long long in place of uint64 for pg<->c++ compat

* Fix a similar compat issue that arrises with the last fix in gcc

* Add 0.3.0 release to CMake (do not create release yet)

* Disable all existing indexes so they can be safely reindexed

* fix indent in usearch

* fix update script for disabling indexes

* remove disable_lantern_indexes from relocation

* Switch to memcpy in all misaligned neighbor list manipulations

* Update cost estimates

* Remove level log stuff and make tests consistently pass on mac and linux

it seems mac and linux generate random numbers somewhat differently
and for some values of M, hnsw level distributions end up affecting
overall index size. This commit addresses that

* Remove unused members of the index header

* Fix unaligned memory write

* Add alignment of 2 for slot type

* simplify matters and get rid of unaligned stack variable

* Remove unused argument to wal_area_reset

* Use uint32 cast for entry slot

* debug sanitizer

* do palloc zero to see why reading zero'th element might cause a panic

* debug

* Fix bug found by address sanitizer

* Suppress unaligned warning and make slot type explicitly unaligned

* suppress unknown pragma warnings and delete duplicate flag

* Error out when inserting into a wal-incompatible index

* suppress compiler warnings in clang

* fix pragma formatting on mac

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.3)
 
-set(LANTERN_VERSION 0.2.7)
+set(LANTERN_VERSION 0.3.0)
 
 project(
   LanternDB
@@ -28,7 +28,7 @@ option(POSTGRES_UBSAN "Turn this on when building with a postgres that has UBSAN
 option(DEV "Developer mode: provide code formatting, get postgres source, etc." OFF)
 option(CODECOVERAGE "Enable code coverage for the build" OFF)
 option(BENCH "Enable benchmarking" OFF)
-option(FAILURE_POINTS "Enable failure points" ON)
+option(FAILURE_POINTS "Enable failure points" OFF)
 option(BUILD_C_TESTS "Build C client tests" OFF)
 
 if (${BUILD_FOR_DISTRIBUTING})
@@ -137,18 +137,18 @@ target_include_directories(
   PRIVATE "./third_party/usearch/c"
   PRIVATE "./third_party/usearch/include/"
   PRIVATE "./third_party/usearch/fp16/include/"
-  PRIVATE "./third_party/usearch/robin-map/include/"
 )
 
 target_compile_options(lantern PRIVATE
     -g
-    -fstack-protector-strong
     -Wformat
     -Werror=format-security
+    -Wno-unknown-pragmas
     -ftree-vectorize
     -fassociative-math
     -fno-signed-zeros
     -fno-trapping-math
+    # -fno-omit-frame-pointer
     -fPIC
 )
 if(${MARCH_NATIVE})
@@ -225,6 +225,8 @@ endif()
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     target_link_options(lantern PRIVATE -static-libstdc++)
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  # it seems -Wno-unknown-pragmas is not enough for clang
+    target_compile_options(lantern PRIVATE "-Wno-unknown-warning-option")
     target_link_options(lantern PRIVATE -static)
 endif ()
 # not sure why, but the above is not enough to force pulling cpp runtime into lantern.so
@@ -276,6 +278,7 @@ set (_update_files
   sql/updates/0.2.4--0.2.5.sql
   sql/updates/0.2.5--0.2.6.sql
   sql/updates/0.2.6--0.2.7.sql
+  sql/updates/0.2.7--0.3.0.sql
 )
 
 # Generate version information for the binary

docker/Dockerfile.dev

@@ -64,14 +64,23 @@ RUN git clone https://github.com/lanterndata/benchmark build/benchmark \
     && pip install -r core/requirements.txt \
     && pip install -r external/requirements.txt
 
+# Install perf
+RUN sudo apt update && sudo apt install -y linux-tools-common linux-tools-generic linux-tools-`uname -r`
+# in host, enable perf_event paranoid via
+# echo -1 | sudo tee /proc/sys/kernel/perf_event_paranoid
+
 ENV DATABASE_URL=postgres://postgres@localhost:5432/postgres
 ENV LANTERN_DATABASE_URL=postgres://postgres@localhost:5432/postgres
 
 # Uncomment the following to change the data directory of the running postgres
 # RUN /usr/local/pgsql/bin/initdb -D /var/lib/postgresql/data
 # RUN echo "listen_addresses '*' " >> /var/lib/postgresql/data/postgresql.conf
 RUN /usr/local/pgsql/bin/initdb -D /var/lib/postgresql/data
-RUN echo "shared_preload_libraries = 'pg_cron,pg_stat_statements' " >> /var/lib/postgresql/data/postgresql.conf
-# RUN echo "host    all             all             0.0.0.0/0               trust" >> /var/lib/postgresql/data/pg_hba.conf
+RUN echo "shared_preload_libraries = 'pg_cron,pg_stat_statements' " >> /var/lib/postgresql/data/postgresql.conf && \
+    echo "wal_level = 'logical' " >> /var/lib/postgresql/data/postgresql.conf && \
+    echo "listen_addresses = '*' " >> /var/lib/postgresql/data/postgresql.conf && \
+    echo "shared_buffers = '4GB' " >> /var/lib/postgresql/data/postgresql.conf
+
+RUN echo "host    all             all             0.0.0.0/0               trust" >> /var/lib/postgresql/data/pg_hba.conf
 # CMD ["/usr/local/pgsql/bin/postgres", "-D", "/var/lib/postgresql/data"]
 CMD ["/usr/local/pgsql/bin/postgres", "-D", "/var/lib/postgresql/data"]

scripts/run_all_tests.sh

@@ -65,9 +65,14 @@ then
        curl -sSo index-sift1k-l2-0.0.0.usearch https://storage.googleapis.com/lanterndata/lanterndb_binary_indexes/index-sift1k-l2-v2.usearch
        curl -sSo index-sift1k-cos.usearch https://storage.googleapis.com/lanterndata/lanterndb_binary_indexes/index-sift1k-cos-v3.usearch
        curl -sSo index-sift1k-l2.usearch https://storage.googleapis.com/lanterndata/lanterndb_binary_indexes/index-sift1k-l2-v3.usearch
-       # Actual index files
+
+       # Outdated index files
        curl -sSo index-sift1k-cos-0.0.13.usearch https://storage.googleapis.com/lanterndata/lanterndb_binary_indexes/index-sift1k-cos-0.0.13.usearch
        curl -sSo index-sift1k-l2sq-0.0.13.usearch https://storage.googleapis.com/lanterndata/lanterndb_binary_indexes/index-sift1k-l2sq-0.0.13.usearch
+
+       # Actual index files
+       curl -sSo index-sift1k-cos-0.3.0.usearch https://storage.googleapis.com/lanterndata/lanterndb_binary_indexes/index-sift1k-cos-0.3.0.usearch
+       curl -sSo index-sift1k-l2sq-0.3.0.usearch https://storage.googleapis.com/lanterndata/lanterndb_binary_indexes/index-sift1k-l2sq-0.3.0.usearch
        # Corrupted index file for test
        tail -c +100 index-sift1k-l2.usearch > index-sift1k-l2-corrupted.usearch
     popd

sql/lantern.sql

@@ -60,9 +60,6 @@ CREATE FUNCTION _lantern_internal.validate_index(index regclass, print_info bool
 CREATE FUNCTION _lantern_internal.failure_point_enable(func TEXT, name TEXT, dont_trigger_first_nr INTEGER DEFAULT 0) RETURNS VOID
 	AS 'MODULE_PATHNAME', 'lantern_internal_failure_point_enable' LANGUAGE C STABLE STRICT PARALLEL UNSAFE;
 
-CREATE FUNCTION _lantern_internal.continue_blockmap_group_initialization(index regclass) RETURNS VOID
-	AS 'MODULE_PATHNAME', 'lantern_internal_continue_blockmap_group_initialization' LANGUAGE C STABLE STRICT PARALLEL UNSAFE;
-
 CREATE FUNCTION _lantern_internal.create_pq_codebook(REGCLASS, NAME, INT, INT, TEXT, INT) RETURNS REAL[][][]
 	AS 'MODULE_PATHNAME', 'create_pq_codebook' LANGUAGE C STABLE STRICT PARALLEL UNSAFE;
 -- operator classes

sql/updates/0.2.7--0.3.0.sql

@@ -0,0 +1,15 @@
+WITH sub as (
+  SELECT indrelid as table_oid, indexrelid, amname
+  FROM pg_class t
+  JOIN pg_index ix ON t.oid = ix.indrelid
+  JOIN pg_class i ON i.oid = ix.indexrelid
+  JOIN pg_am a ON i.relam = a.oid
+  JOIN pg_namespace n ON n.oid = i.relnamespace
+  WHERE a.amname = 'lantern_hnsw'
+)
+UPDATE pg_index ix
+SET indisvalid = false, indisready = false
+FROM sub
+WHERE ix.indexrelid = sub.indexrelid;
+
+DROP FUNCTION IF EXISTS _lantern_internal.continue_blockmap_group_initialization;

src/hnsw.c

@@ -432,13 +432,12 @@ Datum       lantern_internal_failure_point_enable(PG_FUNCTION_ARGS)
     PG_RETURN_VOID();
 }
 
+// todo:: remove in 0.3.1
 PGDLLEXPORT PG_FUNCTION_INFO_V1(lantern_internal_continue_blockmap_group_initialization);
 Datum       lantern_internal_continue_blockmap_group_initialization(PG_FUNCTION_ARGS)
 {
-    Oid indrelid = PG_GETARG_OID(0);
-
-    ldb_continue_blockmap_group_initialization(indrelid);
-    PG_RETURN_VOID();
+    LDB_UNUSED(fcinfo);
+    PG_RETURN_NULL();
 }
 
 PGDLLEXPORT PG_FUNCTION_INFO_V1(lantern_reindex_external_index);

src/hnsw.h

@@ -3,7 +3,9 @@
 
 #include <postgres.h>
 
+#include <assert.h>
 #include <fmgr.h>
+#include <storage/itemptr.h>
 #include <utils/relcache.h>
 
 #define LANTERN_INTERNAL_SCHEMA_NAME "_lantern_internal"
@@ -27,6 +29,28 @@ typedef enum
     UNKNOWN
 } HnswColumnType;
 
+// compilers warn about potential UB when members of this struct are accessed directly
+// though the struct is always accessed via memcpy so the warning does not apply
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpacked-not-aligned"
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpacked-not-aligned"
+
+// C version of uint48_t in c++/usearch
+typedef union __attribute__((__packed__))
+{
+    ItemPointerData itemPointerData;
+    uint32          seqid;
+} ldb_unaligned_slot_union_t;
+
+#pragma clang diagnostic pop
+
+#pragma GCC diagnostic pop
+
+static_assert(sizeof(ldb_unaligned_slot_union_t) >= sizeof(ItemPointerData),
+              "ldb_unaligned_slot_union_t must be large enough for ItemPointerData");
+
 /* Exported functions */
 PGDLLEXPORT void _PG_init(void);
 PGDLLEXPORT void _PG_fini(void);

src/hnsw/build.c

@@ -553,10 +553,9 @@ static void BuildIndex(Relation heap, Relation index, IndexInfo *indexInfo, ldb_
     assert(result_buf != MAP_FAILED);
     //****************************** mmap index to memory END ******************************//
 
-    //****************************** saving to WAL BEGIN ******************************//
+    // save the index to WAL
     UpdateProgress(PROGRESS_CREATEIDX_PHASE, LDB_PROGRESS_HNSW_PHASE_LOAD);
     StoreExternalIndex(index, &metadata, MAIN_FORKNUM, result_buf, &opts, num_added_vectors);
-    //****************************** saving to WAL END ******************************//
 
     munmap_ret = munmap(result_buf, index_file_stat.st_size);
     assert(munmap_ret == 0);

src/hnsw/delete.c

@@ -24,7 +24,6 @@ IndexBulkDeleteResult *ldb_ambulkdelete(IndexVacuumInfo        *info,
     elog(WARNING,
          "LanternDB: hnsw index deletes are currently not implemented. This is a no-op. No memory will be reclaimed");
     // traverse through the index and call the callback for all elements
-    BlockNumber         blockno;
     Buffer              buf;
     HnswIndexHeaderPage header;
     Page                page;
@@ -46,21 +45,18 @@ IndexBulkDeleteResult *ldb_ambulkdelete(IndexVacuumInfo        *info,
         gxlogState = GenericXLogStart(info->index);
         page = GenericXLogRegisterBuffer(gxlogState, buf, LDB_GENERIC_XLOG_DELTA_IMAGE);
         maxoffset = PageGetMaxOffsetNumber(page);
+        // when index is a pq-index, there will be pq header pages that are currently empty
+        // the loop below will skip those. in the future, when those pages are filled up,
+        // we need to add a branch here and skip those pages
 
-        if(isBlockMapBlock(header.blockmap_groups, header.blockmap_groups_nr, blockno)) {
-            ldb_invariant(1 == maxoffset, "expected blockmap page with single item");
-            HnswBlockmapPage *blockmap_page
-                = (HnswBlockmapPage *)PageGetItem(page, PageGetItemId(page, FirstOffsetNumber));
-        } else {
-            for(offset = FirstOffsetNumber; offset <= maxoffset; offset = OffsetNumberNext(offset)) {
-                HnswIndexTuple *nodepage = (HnswIndexTuple *)PageGetItem(page, PageGetItemId(page, offset));
-                unsigned long   label = label_from_node(nodepage->node);
-                label2ItemPointer(label, &tid_data);
-                if(callback(&tid_data, callback_state)) {
-                    block_modified = true;
-                    reset_node_label(nodepage->node);
-                    stats->tuples_removed += 1;
-                }
+        for(offset = FirstOffsetNumber; offset <= maxoffset; offset = OffsetNumberNext(offset)) {
+            HnswIndexTuple *nodepage = (HnswIndexTuple *)PageGetItem(page, PageGetItemId(page, offset));
+            unsigned long   label = label_from_node(nodepage->node);
+            label2ItemPointer(label, &tid_data);
+            if(callback(&tid_data, callback_state)) {
+                block_modified = true;
+                reset_node_label(nodepage->node);
+                stats->tuples_removed += 1;
             }
         }