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Merged
avaitla merged 2 commits into from
Jun 4, 2026
Merged

Report duplicate pk side #7

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d21adbb
table_diff: report which input has duplicate primary keys
avaitla Jun 2, 2026
81fbd17
style: clang-format src/duck_diff_extension.cpp (format-check)
avaitla Jun 4, 2026
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19 changes: 15 additions & 4 deletions src/duck_diff_extension.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -543,15 +543,26 @@ string BuildDiffSQL(const DiffPlan &plan, const string &status_col, const string
}
}

string dup_cond = "EXISTS (SELECT 1 FROM __l GROUP BY " + key_list + " HAVING count(*) > 1) OR " +
"EXISTS (SELECT 1 FROM __r GROUP BY " + key_list + " HAVING count(*) > 1)";
// Detect duplicate keys per side so the error can name which input is at
// fault (and echo the relation text). The relation strings are embedded in
// the message via QuoteLiteral so any quotes/specials are escaped.
string dup_left = "EXISTS (SELECT 1 FROM __l GROUP BY " + key_list + " HAVING count(*) > 1)";
string dup_right = "EXISTS (SELECT 1 FROM __r GROUP BY " + key_list + " HAVING count(*) > 1)";
string msg_both = QuoteLiteral("table_diff: duplicate primary key values found in both the left (" + plan.left +
") and right (" + plan.right + ") inputs");
string msg_left =
QuoteLiteral("table_diff: duplicate primary key values found in the left input (" + plan.left + ")");
string msg_right =
QuoteLiteral("table_diff: duplicate primary key values found in the right input (" + plan.right + ")");
string dup_check = "CASE WHEN " + dup_left + " AND " + dup_right + " THEN error(" + msg_both + ") WHEN " +
dup_left + " THEN error(" + msg_left + ") WHEN " + dup_right + " THEN error(" + msg_right +
") END";

string sql = "WITH __l AS (SELECT __t.*, TRUE AS __p FROM (" + plan.left + ") __t), " +
"__r AS (SELECT __t.*, TRUE AS __p FROM (" + plan.right + ") __t) " + "SELECT " + key_select +
"CASE WHEN r.__p IS NULL THEN 'left_only' WHEN l.__p IS NULL THEN 'right_only' WHEN " + all_eq +
" THEN 'identical' ELSE 'different' END AS " + QuoteIdent(status_col) + middle_select +
" FROM __l AS l FULL OUTER JOIN __r AS r ON " + join_cond + " WHERE (CASE WHEN " + dup_cond +
" THEN error('table_diff: duplicate primary key values found in input') END) IS NULL";
" FROM __l AS l FULL OUTER JOIN __r AS r ON " + join_cond + " WHERE (" + dup_check + ") IS NULL";
return sql;
}

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13 changes: 11 additions & 2 deletions test/sql/table_diff_errors.test
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ INSERT INTO dr VALUES (1, 1);
statement error
SELECT * FROM table_diff('FROM dl', 'FROM dr', pk := 'id');
----
duplicate
duplicate primary key values found in the left input (FROM dl)

# duplicate on the right side is also an error
statement ok
Expand All @@ -62,7 +62,16 @@ INSERT INTO dr VALUES (1, 9);
statement error
SELECT * FROM table_diff('FROM dl', 'FROM dr', pk := 'id');
----
duplicate
duplicate primary key values found in the right input (FROM dr)

# duplicates on both sides are reported together
statement ok
INSERT INTO dl VALUES (1, 7);

statement error
SELECT * FROM table_diff('FROM dl', 'FROM dr', pk := 'id');
----
duplicate primary key values found in both the left (FROM dl) and right (FROM dr) inputs

# ----------------------------------------------------------------------------
# Relation arguments are queries: a bare relation name is rejected, the explicit
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