manifest: make virtual params field of TableMetadata a pointer

This field is also rare and only used for virtual sstables.

Fixes: #2047

Author: annrpom

data_test.go

@@ -1303,7 +1303,7 @@ func runSSTablePropertiesCmd(t *testing.T, td *datadriven.TestData, d *DB) strin
 	props := r.Properties.String()
 	env := sstable.ReadEnv{}
 	if m != nil && m.Virtual {
-		env.Virtual = &m.VirtualParams
+		env.Virtual = m.VirtualParams
 		scaledProps := r.Properties.GetScaledProperties(m.FileBacking.Size, m.Size)
 		props = scaledProps.String()
 	}

file_cache.go

@@ -320,7 +320,7 @@ func createReader(v *fileCacheValue, meta *tableMetadata) (*sstable.Reader, ssta
 				panic("virtual params not initialized")
 			}
 		}
-		env.Virtual = &meta.VirtualParams
+		env.Virtual = meta.VirtualParams
 		env.IsSharedIngested = v.isShared && meta.SyntheticSeqNum() != 0
 	}
 	return r, env
@@ -349,7 +349,7 @@ func (h *fileCacheHandle) withReader(
 				panic("virtual params not initialized")
 			}
 		}
-		env.Virtual = &meta.VirtualParams
+		env.Virtual = meta.VirtualParams
 		env.IsSharedIngested = v.isShared && meta.SyntheticSeqNum() != 0
 	}
 

internal/manifest/version.go

@@ -402,7 +402,7 @@ type TableMetadata struct {
 	// table bounds.
 	boundTypeSmallest, boundTypeLargest boundType
 	// VirtualParams are set only when Virtual is true.
-	VirtualParams virtual.VirtualReaderParams
+	VirtualParams *virtual.VirtualReaderParams
 
 	// SyntheticPrefix is used to prepend a prefix to all keys and/or override all
 	// suffixes in a table; used for some virtual tables.
@@ -614,7 +614,7 @@ func (m *TableMetadata) AttachVirtualBacking(backing *FileBacking) {
 	if m.Smallest().UserKey == nil || m.Largest().UserKey == nil {
 		panic("bounds must be set before attaching backing")
 	}
-	m.VirtualParams = virtual.VirtualReaderParams{
+	m.VirtualParams = &virtual.VirtualReaderParams{
 		Lower:   m.Smallest(),
 		Upper:   m.Largest(),
 		FileNum: m.FileNum,

internal/manifest/version_test.go

@@ -846,7 +846,7 @@ func TestTableMetadataSize(t *testing.T) {
 	}
 	structSize := unsafe.Sizeof(TableMetadata{})
 
-	const tableMetadataSize = 368
+	const tableMetadataSize = 304
 	if structSize != tableMetadataSize {
 		t.Errorf("TableMetadata struct size (%d bytes) is not expected size (%d bytes)",
 			structSize, tableMetadataSize)