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diff --git a/notes/tasks/2020-01-27_cleanup_cdx.md b/notes/tasks/2020-01-27_cleanup_cdx.md
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+
+Accidentally seem to have backfilled many CDX lines with non-PDF content.
+Should clear these out!
+
+Something like:
+
+    mimetype = 'text/html'
+    not in file_meta
+
+Or maybe instead:
+
+    mimetype = 'text/html'
+    not in file_meta
+
+SQL:
+
+    SELECT *        FROM cdx WHERE mimetype = 'text/html' AND row_created < '2019-10-01' LIMIT 5;
+    SELECT COUNT(1) FROM cdx WHERE mimetype = 'text/html' AND row_created < '2019-10-01';
+    => 24841846
+
+    SELECT *        FROM cdx LEFT JOIN file_meta ON file_meta.sha1hex = cdx.sha1hex WHERE cdx.mimetype = 'text/html' AND file_meta.sha256hex IS NULL LIMIT 5;
+    SELECT COUNT(1) FROM cdx LEFT JOIN file_meta ON cdx.sha1hex = file_meta.sha1hex WHERE cdx.mimetype = 'text/html' AND file_meta.sha256hex IS NULL;
+    => 24547552
+
+    DELETE FROM cdx
+      WHERE sha1hex IN
+      (SELECT cdx.sha1hex
+       FROM cdx
+       LEFT JOIN file_meta ON file_meta.sha1hex = cdx.sha1hex
+       WHERE cdx.mimetype = 'text/html' AND file_meta.sha256hex IS NULL);
+    => DELETE 24553428
+
+Slightly more... probably should have had a "AND cdx.mimetype = 'text/html'" in
+the DELETE WHERE clause.