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Add VisibilityBitmap to TableMapEvent in replication #813

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merged 4 commits into from
Aug 24, 2023
Merged

Add VisibilityBitmap to TableMapEvent in replication #813

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ccabd26
Add `VisibilityBitmap` to `TableMapEvent` for MySQL 8.0.23+ Invisible…
dongwook-chan Aug 15, 2023
6260982
Refactor bitmap iteration to align with MySQL source code
dongwook-chan Aug 15, 2023
cac73e6
Add test for column visibility in table map
dongwook-chan Aug 19, 2023
b55ff1d
Add test case 2 for column visibility in table map
dongwook-chan Aug 20, 2023
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1 change: 1 addition & 0 deletions replication/const.go
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Original file line number Diff line number Diff line change
Expand Up @@ -240,6 +240,7 @@ const (
TABLE_MAP_OPT_META_PRIMARY_KEY_WITH_PREFIX
TABLE_MAP_OPT_META_ENUM_AND_SET_DEFAULT_CHARSET
TABLE_MAP_OPT_META_ENUM_AND_SET_COLUMN_CHARSET
TABLE_MAP_OPT_META_COLUMN_VISIBILITY
)

type IntVarEventType byte
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26 changes: 26 additions & 0 deletions replication/row_event.go
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,9 @@ type TableMapEvent struct {
// EnumSetDefaultCharset/EnumSetColumnCharset is similar to DefaultCharset/ColumnCharset but for enum/set columns.
EnumSetDefaultCharset []uint64
EnumSetColumnCharset []uint64

// VisibilityBitmap stores bits that are set if corresponding column is not invisible (MySQL 8.0.23+)
VisibilityBitmap []byte
}

func (e *TableMapEvent) Decode(data []byte) error {
Expand Down Expand Up @@ -312,6 +315,9 @@ func (e *TableMapEvent) decodeOptionalMeta(data []byte) (err error) {
return err
}

case TABLE_MAP_OPT_META_COLUMN_VISIBILITY:
e.VisibilityBitmap = v

default:
// Ignore for future extension
}
Expand Down Expand Up @@ -421,6 +427,7 @@ func (e *TableMapEvent) Dump(w io.Writer) {
fmt.Fprintf(w, "Primary key prefix: %v\n", e.PrimaryKeyPrefix)
fmt.Fprintf(w, "Enum/set default charset: %v\n", e.EnumSetDefaultCharset)
fmt.Fprintf(w, "Enum/set column charset: %v\n", e.EnumSetColumnCharset)
fmt.Fprintf(w, "Invisible Column bitmap: \n%s", hex.Dump(e.VisibilityBitmap))

unsignedMap := e.UnsignedMap()
fmt.Fprintf(w, "UnsignedMap: %#v\n", unsignedMap)
Expand All @@ -440,6 +447,9 @@ func (e *TableMapEvent) Dump(w io.Writer) {
geometryTypeMap := e.GeometryTypeMap()
fmt.Fprintf(w, "GeometryTypeMap: %#v\n", geometryTypeMap)

visibilityMap := e.VisibilityMap()
fmt.Fprintf(w, "VisibilityMap: %#v\n", visibilityMap)

nameMaxLen := 0
for _, name := range e.ColumnName {
if len(name) > nameMaxLen {
Expand Down Expand Up @@ -730,6 +740,22 @@ func (e *TableMapEvent) GeometryTypeMap() map[int]uint64 {
return ret
}

// VisibilityMap returns a map: column index -> visiblity.
// Invisible column was introduced in MySQL 8.0.23
// nil is returned if not available.
func (e *TableMapEvent) VisibilityMap() map[int]bool {
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As for testing, I think maybe you can capture/construct some VisibilityBitmap bytes and test the result of TableMapEvent.VisibilityMap is expected.

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@lance6716
Sure. I think I should create a separate function. Just as TestTableMapOptMetaPrimaryKey is defined solely for primary key type meta data. At first, I thought about squeezing into TestTableMapOptMetaNames or TestTableMapHelperMaps, but it's too packed and I saw no room for any addition. Your advice would be help me a lot. 😀

if len(e.VisibilityBitmap) == 0 {
return nil
}
p := 0
ret := make(map[int]bool)
for i := 0; i < int(e.ColumnCount); i++ {
ret[i] = e.VisibilityBitmap[p/8]&(1<<uint(7-p%8)) != 0
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nit: Maybe it's a little easier to understand the original code with countdown instead of 1<<uint(7-p%8)

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@dongwook-chan dongwook-chan Aug 15, 2023 •
edited
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@atercattus
I appreciate your review. Also, I agree with you and I can get this fixed.
Actually VisibilityMap is copy and paste of existing UnsignedMap. Should I fix UnsignedMap too?
I could create a separate PR it if it seems irrelevant to this PR.

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Oh. @lance6716 what do you think about this? Apply the Boy Scout Rule or not?

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If we decide to improve, the code will look like below.

func (e *TableMapEvent) VisibilityMap() map[int]bool {
	if len(e.VisibilityBitmap) == 0 {
		return nil
	}
	ret := make(map[int]bool)
	for _, field := range e.VisibilityBitmap {
		for c, i := 0x80, 0; c != 0; c, i = c>>1, i+1 {
			ret[i] = field&byte(c) != 0
		}
	}
	return ret
}

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The old code is really not easy to understand 😢 I also hope we start to improve the readability. As for UnsignedMap, I'm OK that you also modify it in this PR or another PR. WDYT @atercattus

Your new code snippet seems not optimal. The status of i should be kept when iterate bytes of VisibilityBitmap. And we can early stop when the column count is not a multiple of 8 (though the original code seems not optimize about this). Maybe we can

...
i := 0
for e.VisibilityBitmap {
  for c := 0x80; ... {
    ret[i] = ...
    i++
    if i >= e.ColumnCount { return }
  }
}
...

Welcome to find different code

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@dongwook-chan dongwook-chan Aug 15, 2023 •
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My bad. i should indeed be initialized outside of the inner loop.

p++
}
return ret
}

// Below realType and IsXXXColumn are base from:
// table_def::type in sql/rpl_utility.h
// Table_map_log_event::print_columns in mysql-8.0/sql/log_event.cc and mariadb-10.5/sql/log_event_client.cc
Expand Down