feat: support clean read base on fast mode (#5371)

ref #5252

dbms/src/Storages/DeltaMerge/DMDecoratorStreams.h

@@ -22,7 +22,6 @@
 
 #include <unordered_set>
 
-
 namespace DB
 {
 namespace DM

dbms/src/Storages/DeltaMerge/File/DMFileBlockInputStream.cpp

@@ -61,6 +61,7 @@ DMFileBlockInputStreamPtr DMFileBlockInputStreamBuilder::build(const DMFilePtr &
         read_columns,
         is_common_handle,
         enable_clean_read,
+        is_fast_mode,
         max_data_version,
         std::move(pack_filter),
         mark_cache,

dbms/src/Storages/DeltaMerge/File/DMFileBlockInputStream.h

@@ -69,14 +69,18 @@ class DMFileBlockInputStreamBuilder
 
     // **** filters **** //
 
-    // Only set this param to true when
-    // 1. There is no delta.
-    // 2. You don't need pk, version and delete_tag columns
+    // Only set enable param to true when
+    // in normal mode:
+    //    1. There is no delta.
+    //    2. You don't need pk, version and delete_tag columns
+    // in fast mode:
+    //    1. You don't need pk columns
     // If you have no idea what it means, then simply set it to false.
     // `max_data_version_` is the MVCC filter version for reading. Used by clean read check
-    DMFileBlockInputStreamBuilder & enableCleanRead(bool enable, UInt64 max_data_version_)
+    DMFileBlockInputStreamBuilder & enableCleanRead(bool enable, bool is_fast_mode_, UInt64 max_data_version_)
     {
         enable_clean_read = enable;
+        is_fast_mode = is_fast_mode_;
         max_data_version = max_data_version_;
         return *this;
     }
@@ -139,6 +143,7 @@ class DMFileBlockInputStreamBuilder
 
     // clean read
     bool enable_clean_read = false;
+    bool is_fast_mode = false;
     UInt64 max_data_version = std::numeric_limits<UInt64>::max();
     // Rough set filter
     RSOperatorPtr rs_filter;
@@ -150,8 +155,8 @@ class DMFileBlockInputStreamBuilder
     bool enable_column_cache = false;
     ColumnCachePtr column_cache;
     ReadLimiterPtr read_limiter;
-    size_t aio_threshold;
-    size_t max_read_buffer_size;
+    size_t aio_threshold{};
+    size_t max_read_buffer_size{};
     size_t rows_threshold_per_read = DMFILE_READ_ROWS_THRESHOLD;
     bool read_one_pack_every_time = false;
 

dbms/src/Storages/DeltaMerge/File/DMFileReader.cpp

@@ -25,6 +25,8 @@
 #include <Storages/Page/PageUtil.h>
 #include <fmt/format.h>
 
+#include <string>
+
 namespace CurrentMetrics
 {
 extern const Metric OpenFileForRead;
@@ -210,6 +212,7 @@ DMFileReader::DMFileReader(
     bool is_common_handle_,
     // clean read
     bool enable_clean_read_,
+    bool is_fast_mode_,
     UInt64 max_read_version_,
     // filters
     DMFilePackFilter && pack_filter_,
@@ -230,6 +233,7 @@ DMFileReader::DMFileReader(
     , read_one_pack_every_time(read_one_pack_every_time_)
     , single_file_mode(dmfile_->isSingleFileMode())
     , enable_clean_read(enable_clean_read_)
+    , is_fast_mode(is_fast_mode_)
     , max_read_version(max_read_version_)
     , pack_filter(std::move(pack_filter_))
     , skip_packs_by_column(read_columns.size(), 0)
@@ -338,13 +342,16 @@ Block DMFileReader::read()
     }
 
     // TODO: this will need better algorithm: we should separate those packs which can and can not do clean read.
-    bool do_clean_read = enable_clean_read && expected_handle_res == All && not_clean_rows == 0;
-    if (do_clean_read)
+    bool do_clean_read_on_normal_mode = enable_clean_read && expected_handle_res == All && not_clean_rows == 0 && (!is_fast_mode);
+
+    bool do_clean_read_on_handle = enable_clean_read && is_fast_mode && expected_handle_res == All;
+
+    if (do_clean_read_on_normal_mode)
     {
         UInt64 max_version = 0;
         for (size_t pack_id = start_pack_id; pack_id < next_pack_id; ++pack_id)
             max_version = std::max(pack_filter.getMaxVersion(pack_id), max_version);
-        do_clean_read = max_version <= max_read_version;
+        do_clean_read_on_normal_mode = max_version <= max_read_version;
     }
 
     for (size_t i = 0; i < read_columns.size(); ++i)
@@ -353,7 +360,24 @@ Block DMFileReader::read()
         {
             // For clean read of column pk, version, tag, instead of loading data from disk, just create placeholder column is OK.
             auto & cd = read_columns[i];
-            if (do_clean_read && isExtraColumn(cd))
+            if (cd.id == EXTRA_HANDLE_COLUMN_ID && do_clean_read_on_handle)
+            {
+                // Return the first row's handle
+                ColumnPtr column;
+                if (is_common_handle)
+                {
+                    StringRef min_handle = pack_filter.getMinStringHandle(start_pack_id);
+                    column = cd.type->createColumnConst(read_rows, Field(min_handle.data, min_handle.size));
+                }
+                else
+                {
+                    Handle min_handle = pack_filter.getMinHandle(start_pack_id);
+                    column = cd.type->createColumnConst(read_rows, Field(min_handle));
+                }
+                res.insert(ColumnWithTypeAndName{column, cd.type, cd.name, cd.id});
+                skip_packs_by_column[i] = read_packs;
+            }
+            else if (do_clean_read_on_normal_mode && isExtraColumn(cd))
             {
                 ColumnPtr column;
                 if (cd.id == EXTRA_HANDLE_COLUMN_ID)
@@ -441,6 +465,7 @@ Block DMFileReader::read()
                         auto column = data_type->createColumn();
                         readFromDisk(cd, column, start_pack_id, read_rows, skip_packs_by_column[i], single_file_mode);
                         auto converted_column = convertColumnByColumnDefineIfNeed(data_type, std::move(column), cd);
+
                         res.insert(ColumnWithTypeAndName{std::move(converted_column), cd.type, cd.name, cd.id});
                         skip_packs_by_column[i] = 0;
                     }
@@ -456,6 +481,7 @@ Block DMFileReader::read()
                         dmfile->path());
                     // New column after ddl is not exist in this DMFile, fill with default value
                     ColumnPtr column = createColumnWithDefaultValue(cd, read_rows);
+
                     res.insert(ColumnWithTypeAndName{std::move(column), cd.type, cd.name, cd.id});
                     skip_packs_by_column[i] = 0;
                 }

dbms/src/Storages/DeltaMerge/File/DMFileReader.h

@@ -76,6 +76,7 @@ class DMFileReader
         // 2. You don't need pk, version and delete_tag columns
         // If you have no idea what it means, then simply set it to false.
         bool enable_clean_read_,
+        bool is_fast_mode_,
         // The the MVCC filter version. Used by clean read check.
         UInt64 max_read_version_,
         // filters
@@ -122,8 +123,10 @@ class DMFileReader
     const bool single_file_mode;
 
     /// Clean read optimize
-    // If there is no delta for some packs in stable, we can try to do clean read.
+    // In normal mode, if there is no delta for some packs in stable, we can try to do clean read.
+    // In fast mode, we always try to do clean read.
     const bool enable_clean_read;
+    const bool is_fast_mode;
     const UInt64 max_read_version;
 
     /// Filters

dbms/src/Storages/DeltaMerge/Segment.cpp

@@ -514,6 +514,8 @@ BlockInputStreamPtr Segment::getInputStreamRaw(const DMContext & dm_context,
                                                bool filter_delete_mark,
                                                size_t expected_block_size)
 {
+    /// Now, we use filter_delete_mark to determine whether it is in fast mode or just from `selraw * xxxx`
+    /// But this way seems not to be robustness enough, maybe we need another flag?
     auto new_columns_to_read = std::make_shared<ColumnDefines>();
 
 
@@ -523,20 +525,37 @@ BlockInputStreamPtr Segment::getInputStreamRaw(const DMContext & dm_context,
         new_columns_to_read->push_back(getTagColumnDefine());
     }
 
+    bool enable_clean_read = filter_delete_mark;
+
     for (const auto & c : columns_to_read)
     {
-        if (c.id != EXTRA_HANDLE_COLUMN_ID && (!(filter_delete_mark && c.id == TAG_COLUMN_ID)))
-            new_columns_to_read->push_back(c);
+        if (c.id != EXTRA_HANDLE_COLUMN_ID)
+        {
+            if (!(filter_delete_mark && c.id == TAG_COLUMN_ID))
+                new_columns_to_read->push_back(c);
+        }
+        else
+        {
+            enable_clean_read = false;
+        }
     }
 
+    /// when we read in fast mode, if columns_to_read does not include EXTRA_HANDLE_COLUMN_ID,
+    /// we can try to use clean read to make optimization in stable part.
+    /// when the pack is under totally data_ranges and has no rows whose del_mark = 1 --> we don't need read handle_column/tag_column/version_column
+    /// when the pack is under totally data_ranges and has rows whose del_mark = 1 --> we don't need read handle_column/version_column
+    /// others --> we don't need read version_column
+    /// Considering the del min max index has some problem now, we first only optimize with handle column.
+
     BlockInputStreamPtr stable_stream = segment_snap->stable->getInputStream(
         dm_context,
         *new_columns_to_read,
         data_ranges,
         filter,
         std::numeric_limits<UInt64>::max(),
         expected_block_size,
-        false);
+        /* enable_clean_read */ enable_clean_read,
+        /* is_fast_mode */ filter_delete_mark);
 
     BlockInputStreamPtr delta_stream = std::make_shared<DeltaValueInputStream>(dm_context, segment_snap->delta, new_columns_to_read, this->rowkey_range);
 

dbms/src/Storages/DeltaMerge/StableValueSpace.cpp

@@ -328,7 +328,8 @@ StableValueSpace::Snapshot::getInputStream(
     const RSOperatorPtr & filter,
     UInt64 max_data_version,
     size_t expected_block_size,
-    bool enable_clean_read)
+    bool enable_clean_read,
+    bool is_fast_mode)
 {
     LOG_FMT_DEBUG(log, "max_data_version: {}, enable_clean_read: {}", max_data_version, enable_clean_read);
     SkippableBlockInputStreams streams;
@@ -337,7 +338,7 @@ StableValueSpace::Snapshot::getInputStream(
     {
         DMFileBlockInputStreamBuilder builder(context.db_context);
         builder
-            .enableCleanRead(enable_clean_read, max_data_version)
+            .enableCleanRead(enable_clean_read, is_fast_mode, max_data_version)
             .setRSOperator(filter)
             .setColumnCache(column_caches[i])
             .setTracingID(context.tracing_id)

dbms/src/Storages/DeltaMerge/StableValueSpace.h

@@ -150,7 +150,8 @@ class StableValueSpace : public std::enable_shared_from_this<StableValueSpace>
                                                     const RSOperatorPtr & filter,
                                                     UInt64 max_data_version,
                                                     size_t expected_block_size,
-                                                    bool enable_clean_read);
+                                                    bool enable_clean_read,
+                                                    bool is_fast_mode = false);
 
         RowsAndBytes getApproxRowsAndBytes(const DMContext & context, const RowKeyRange & range) const;