From 7825b3c6f019fe501c1fbfd534e53e00766750d1 Mon Sep 17 00:00:00 2001
From: Dimitri Yatsenko <dimitri.yatsenko@gmail.com>
Date: Sun, 11 Jan 2026 18:19:52 -0600
Subject: [PATCH] enhance: Show codec names in table preview instead of =BLOB=

- Raw blobs (no codec) now show "bytes"
- Raw json (no codec) shows "json"
- Codec fields show "<codec_name>" (e.g., <blob>, <hash>, <object>)
- HTML output properly escapes angle brackets for browser display
- Improves clarity when viewing table contents

Example output:
  *id    raw_blob  blob_data  json_data
  1      bytes     <blob>     json

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 src/datajoint/preview.py | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/datajoint/preview.py b/src/datajoint/preview.py
index 8cca46b2a..c0f103eb1 100644
--- a/src/datajoint/preview.py
+++ b/src/datajoint/preview.py
@@ -24,6 +24,21 @@ def _format_object_display(json_data):
         return "=OBJ[file]="
 
 
+def _get_blob_placeholder(heading, field_name, html_escape=False):
+    """Get display placeholder for a blob/json field based on its codec."""
+    attr = heading.attributes.get(field_name)
+    if attr is None:
+        return "bytes"
+    if attr.codec is not None:
+        name = attr.codec.name
+        if html_escape:
+            return f"&lt;{name}&gt;"
+        return f"<{name}>"
+    if attr.json:
+        return "json"
+    return "bytes"
+
+
 def preview(query_expression, limit, width):
     heading = query_expression.heading
     rel = query_expression.proj(*heading.non_blobs)
@@ -55,7 +70,7 @@ def preview(query_expression, limit, width):
     def get_placeholder(f):
         if f in object_fields:
             return "=OBJ[.xxx]="
-        return "=BLOB="
+        return _get_blob_placeholder(heading, f)
 
     widths = {
         f: min(
@@ -72,7 +87,7 @@ def get_display_value(tup, f, idx):
         elif f in object_fields and idx < len(object_data_list):
             return _format_object_display(object_data_list[idx].get(f))
         else:
-            return "=BLOB="
+            return _get_blob_placeholder(heading, f)
 
     return (
         " ".join([templates[f] % ("*" + f if f in rel.primary_key else f) for f in columns])
@@ -113,7 +128,7 @@ def get_html_display_value(tup, name, idx):
         elif name in object_fields and idx < len(object_data_list):
             return _format_object_display(object_data_list[idx].get(name))
         else:
-            return "=BLOB="
+            return _get_blob_placeholder(heading, name, html_escape=True)
 
     css = """
     <style type="text/css">