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Support Nullable(JSON) in ClickHouse #3626

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Support Nullable(JSON) in ClickHouse #3626

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ac44264
fix: support nullable json in clickhouse
aldofunes Oct 24, 2025
f7665a6
Merge branch 'PeerDB-io:main' into main
aldofunes Oct 24, 2025
4babae7
fix: extract nullable string before casting to nullable json
aldofunes Nov 5, 2025
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2 changes: 1 addition & 1 deletion flow/connectors/clickhouse/clickhouse.go
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Original file line number Diff line number Diff line change
Expand Up @@ -446,7 +446,7 @@ func GetTableSchemaForTable(tm *protos.TableMapping, columns []driver.ColumnType
qkind = types.QValueKindArrayBoolean
case "Array(Date)":
qkind = types.QValueKindArrayDate
case "JSON":
case "JSON", "Nullable(JSON)":
qkind = types.QValueKindJSON
default:
if strings.Contains(column.DatabaseTypeName(), "Decimal") {
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15 changes: 14 additions & 1 deletion flow/connectors/clickhouse/normalize_query.go
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Original file line number Diff line number Diff line change
Expand Up @@ -193,7 +193,7 @@ func (t *NormalizeQueryGenerator) BuildQuery(ctx context.Context) (string, error
peerdb_clickhouse.QuoteIdentifier(dstColName),
)
}
case "JSON", "Nullable(JSON)":
case "JSON":
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@jgao54 jgao54 Nov 13, 2025

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Can be combined into:

Suggested change
case "JSON":
case "JSON", "Nullable(JSON)":
stringType := strings.Replace(clickHouseType, "JSON", "String", 1)
fmt.Fprintf(&projection,
"JSONExtract(_peerdb_data, %s, '%s')::%s AS %s,",
peerdb_clickhouse.QuoteLiteral(colName),
stringType,
clickHouseType,
peerdb_clickhouse.QuoteIdentifier(dstColName),
)
if t.enablePrimaryUpdate {
fmt.Fprintf(&projectionUpdate,
"JSONExtract(_peerdb_match_data, %s, '%s')::%s AS %s,",
peerdb_clickhouse.QuoteLiteral(colName),
stringType,
clickHouseType,
peerdb_clickhouse.QuoteIdentifier(dstColName),
)
}

fmt.Fprintf(&projection,
"JSONExtractString(_peerdb_data, %s)::JSON AS %s,",
peerdb_clickhouse.QuoteLiteral(colName),
Expand All @@ -206,6 +206,19 @@ func (t *NormalizeQueryGenerator) BuildQuery(ctx context.Context) (string, error
peerdb_clickhouse.QuoteIdentifier(dstColName),
)
}
case "Nullable(JSON)":
fmt.Fprintf(&projection,
"JSONExtract(_peerdb_data, %s, 'Nullable(String)')::Nullable(JSON) AS %s,",
peerdb_clickhouse.QuoteLiteral(colName),
peerdb_clickhouse.QuoteIdentifier(dstColName),
)
if t.enablePrimaryUpdate {
fmt.Fprintf(&projectionUpdate,
"JSONExtract(_peerdb_match_data, %s, 'Nullable(String)')::Nullable(JSON) AS %s,",
peerdb_clickhouse.QuoteLiteral(colName),
peerdb_clickhouse.QuoteIdentifier(dstColName),
)
}

default:
projLen := projection.Len()
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4 changes: 4 additions & 0 deletions flow/connectors/clickhouse/table_function.go
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,10 @@ func jsonFieldExpressionConverter(
return sourceFieldIdentifier, nil
}

if field.Nullable {
return fmt.Sprintf("CAST(%s, 'Nullable(JSON)')", sourceFieldIdentifier), nil
}

return fmt.Sprintf("CAST(%s, 'JSON')", sourceFieldIdentifier), nil
}

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