From 490d5a2c8349dead00fa2d81601d748c18ea2bed Mon Sep 17 00:00:00 2001
From: Michael Wilkinson <miwilkin@syr.edu>
Date: Fri, 6 Mar 2020 14:13:33 -0500
Subject: [PATCH] [Docs] further clarification on the case of TTrees
---
core/base/src/TObject.cxx | 5 ++++-
io/io/src/TDirectoryFile.cxx | 4 +---
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/core/base/src/TObject.cxx b/core/base/src/TObject.cxx
index c17cea47ed0..93923671ad8 100644
--- a/core/base/src/TObject.cxx
+++ b/core/base/src/TObject.cxx
@@ -752,7 +752,10 @@ void TObject::UseCurrentStyle()
/// is safer than kOverwrite but it is slower.
/// NOTE: Neither kOverwrite nor kWriteDelete reduces the size of a TFile--
/// the space is simply freed up to be overwritten; in the case of a TTree,
-/// only the metadata is replaced, effectively making the data invisible
+/// it is more complicated. If one opens a TTree, appends some entries,
+/// then writes it out, the behaviour is effectively the same. If, however,
+/// one creates a new TTree and writes it out in this way,
+/// only the metadata is replaced, effectively making the old data invisible
/// without deleting it.
/// The kSingleKey option is only used by TCollection::Write() to write
/// a container with a single key instead of each object in the container
diff --git a/io/io/src/TDirectoryFile.cxx b/io/io/src/TDirectoryFile.cxx
index 0ceac876544..15ae3e635c1 100644
--- a/io/io/src/TDirectoryFile.cxx
+++ b/io/io/src/TDirectoryFile.cxx
@@ -1233,9 +1233,7 @@ TDirectory *TDirectoryFile::mkdir(const char *name, const char *title, Bool_t re
/// By default, only the highest cycle of a key is kept. Keys for which
/// the "KEEP" flag has been set are not removed. See TKey::Keep().
/// NOTE: This does not reduce the size of a TFile--
-/// the space is simply freed up to be overwritten; in the case of a TTree,
-/// only the metadata is replaced, effectively making the data invisible
-/// without deleting it.
+/// the space is simply freed up to be overwritten.
void TDirectoryFile::Purge(Short_t)
{
--
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