[PATCH 29/28] cindex: --prune checkpoints to avoid OOM

[Eric Wong]

Having many ->delete_document calls in a transaction still
causes Xapian to eat up a large amount of memory and OOM on my
system.

I may reimplement --prune to avoid blocking ongoing updates, but
this is a simple fix for swapping and OOMs for now.
---
 lib/PublicInbox/CodeSearchIdx.pm | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/lib/PublicInbox/CodeSearchIdx.pm b/lib/PublicInbox/CodeSearchIdx.pm
index 704baa9c..e353f452 100644
--- a/lib/PublicInbox/CodeSearchIdx.pm
+++ b/lib/PublicInbox/CodeSearchIdx.pm
@@ -622,12 +622,21 @@ sub scan_git_dirs ($) {
 
 sub prune_cb { # git->check_async callback
        my ($hex, $type, undef, $self_id) = @_;
-       if ($type ne 'commit') {
-               my ($self, $id) = @$self_id;
-               progress($self, "$hex $type");
-               ++$self->{pruned};
-               $self->{xdb}->delete_document($id);
-       }
+       return if $type eq 'commit';
+       my ($self, $id) = @$self_id;
+       my $len = $self->{xdb}->get_doclength($id);
+       progress($self, "$hex $type (doclength=$len)");
+       ++$self->{pruned};
+       $self->{xdb}->delete_document($id);
+
+       # all math around batch_bytes calculation is pretty fuzzy,
+       # but need a way to regularly flush output to avoid OOM,
+       # so assume the average term + position overhead is the
+       # answer to everything: 42
+       return if ($self->{batch_bytes} -= ($len * 42)) > 0;
+       cidx_ckpoint($self, "[$self->{shard}] $self->{pruned}");
+       $self->{batch_bytes} = $self->{-opt}->{batch_size} //
+                       $PublicInbox::SearchIdx::BATCH_BYTES;
 }
 
 sub shard_prune { # via wq_io_do
@@ -639,6 +648,8 @@ sub shard_prune { # via wq_io_do
        my $cur = $xdb->postlist_begin('Tc');
        my $end = $xdb->postlist_end('Tc');
        my ($id, @cmt, $oid);
+       local $self->{batch_bytes} = $self->{-opt}->{batch_size} //
+                               $PublicInbox::SearchIdx::BATCH_BYTES;
        local $self->{pruned} = 0;
        for (; $cur != $end && !$DO_QUIT; $cur++) {
                @cmt = xap_terms('Q', $xdb, $id = $cur->get_docid);