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Show codec names in table preview instead of =BLOB= #1330

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Merged
dimitri-yatsenko merged 1 commit into from
Jan 12, 2026
Merged

Show codec names in table preview instead of =BLOB= #1330

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21 changes: 18 additions & 3 deletions src/datajoint/preview.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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"
Comment on lines +30 to +31
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@ttngu207 ttngu207 Jan 12, 2026

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Why do we expect attr to be None? Can it ever be None? If it can, perhaps this should raise an error instead of returning bytes

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@dimitri-yatsenko dimitri-yatsenko Jan 12, 2026

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Good catch! You're right - attr should never be None here since field_name always comes from heading.names. The defensive check was silently hiding potential bugs.

I've updated the code in PR #1331 (which now includes this PR) to raise an error instead:

if attr is None:
    raise DataJointError(f"Field '{field_name}' not found in heading")

This way any unexpected state will surface immediately rather than returning a misleading "bytes" placeholder.

if attr.codec is not None:
name = attr.codec.name
if html_escape:
return f"<{name}>"
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)
Expand Down Expand Up @@ -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(
Expand All @@ -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])
Expand Down Expand Up @@ -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">
Expand Down
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