diff --git a/sql/upgrades/121.sql b/sql/upgrades/121.sql
new file mode 100644
--- /dev/null
+++ b/sql/upgrades/121.sql
@@ -0,0 +1,10 @@
+-- SWH Indexer DB schema upgrade
+-- from_version: 120
+-- to_version: 121
+-- description: add comment to the 'mappings' column
+
+insert into dbversion(version, release, description)
+values(121, now(), 'Work In Progress');
+
+comment on column revision_metadata.mappings is 'type of metadata files used to obtain this metadata (eg. pkg-info, npm)';
+comment on column origin_intrinsic_metadata.mappings is 'type of metadata files used to obtain this metadata (eg. pkg-info, npm)';
diff --git a/swh/indexer/sql/30-swh-schema.sql b/swh/indexer/sql/30-swh-schema.sql
--- a/swh/indexer/sql/30-swh-schema.sql
+++ b/swh/indexer/sql/30-swh-schema.sql
@@ -14,7 +14,7 @@
 );
 
 insert into dbversion(version, release, description)
-      values(119, now(), 'Work In Progress');
+      values(121, now(), 'Work In Progress');
 -- Computing metadata on sha1's contents
 
 -- a SHA1 checksum (not necessarily originating from Git)
@@ -126,6 +126,7 @@
 comment on column revision_metadata.id is 'sha1_git of revision';
 comment on column revision_metadata.translated_metadata is 'result of detection and translation with defined format';
 comment on column revision_metadata.indexer_configuration_id is 'tool used for detection';
+comment on column revision_metadata.mappings is 'type of metadata files used to obtain this metadata (eg. pkg-info, npm)';
 
 create table origin_intrinsic_metadata(
   origin_id                 bigserial  not null,
@@ -141,3 +142,4 @@
 comment on column origin_intrinsic_metadata.metadata is 'metadata extracted from a revision';
 comment on column origin_intrinsic_metadata.indexer_configuration_id is 'tool used to generate this metadata';
 comment on column origin_intrinsic_metadata.from_revision is 'sha1 of the revision this metadata was copied from.';
+comment on column origin_intrinsic_metadata.mappings is 'type of metadata files used to obtain this metadata (eg. pkg-info, npm)';