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Aug 21, 2025
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mongo: improve documentation to handle nested object #4311

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32 changes: 18 additions & 14 deletions docs/integrations/data-ingestion/clickpipes/mongodb/quickstart.md
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,18 @@ FROM t1;
└─────────────────────────┴────────────────────────────────┘
```

When querying _nested object fields_ using dot syntax, make sure to add the [`^`](https://clickhouse.com/docs/sql-reference/data-types/newjson#reading-json-sub-objects-as-sub-columns) operator:

```sql title="Query"
SELECT _full_document.^shipping as shipping_info FROM t1;
```

```shell title="Result"
┌─shipping_info──────────────────────────────────────┐
│ {"city":"Seattle","cost":19.99,"method":"express"} │
└────────────────────────────────────────────────────┘
```

### Dynamic type {#dynamic-type}

In ClickHouse, each field in JSON has `Dynamic` type. Dynamic type allows ClickHouse to store values of any type without knowing the type in advance. You can verify this with the `toTypeName` function:
Expand Down Expand Up @@ -218,9 +230,7 @@ SELECT
CAST(_full_document.status, 'String') AS status,
CAST(_full_document.total_amount, 'Decimal64(2)') AS total_amount,
CAST(parseDateTime64BestEffortOrNull(_full_document.order_date, 3), 'DATETIME(3)') AS order_date,
CAST(_full_document.shipping.method, 'String') AS shipping_method,
CAST(_full_document.shipping.city, 'String') AS shipping_city,
CAST(_full_document.shipping.cost, 'Decimal64(2)') AS shipping_cost,
_full_document.^shipping AS shipping_info,
_full_document.items AS items
FROM t1 FINAL
WHERE _peerdb_is_deleted = 0;
Expand All @@ -236,9 +246,7 @@ This view will have the following schema:
│ status │ String │
│ total_amount │ Decimal(18, 2) │
│ order_date │ DateTime64(3) │
│ shipping_method │ String │
│ shipping_city │ String │
│ shipping_cost │ Decimal(18, 2) │
│ shipping_info │ JSON │
│ items │ Dynamic │
└─────────────────┴────────────────┘
```
Expand All @@ -250,7 +258,7 @@ SELECT
customer_id,
sum(total_amount)
FROM v1
WHERE shipping_city = 'Seattle'
WHERE shipping_info.city = 'Seattle'
GROUP BY customer_id
ORDER BY customer_id DESC
LIMIT 10;
Expand All @@ -272,9 +280,7 @@ CREATE TABLE flattened_t1 (
`status` String,
`total_amount` Decimal(18, 2),
`order_date` DateTime64(3),
`shipping_method` String,
`shipping_city` String,
`shipping_cost` Decimal(18, 2),
`shipping_info` JSON,
`items` Dynamic
)
ENGINE = ReplacingMergeTree()
Expand All @@ -289,9 +295,7 @@ SELECT
CAST(_full_document.status, 'String') AS status,
CAST(_full_document.total_amount, 'Decimal64(2)') AS total_amount,
CAST(parseDateTime64BestEffortOrNull(_full_document.order_date, 3), 'DATETIME(3)') AS order_date,
CAST(_full_document.shipping.method, 'String') AS shipping_method,
CAST(_full_document.shipping.city, 'String') AS shipping_city,
CAST(_full_document.shipping.cost, 'Decimal64(2)') AS shipping_cost,
_full_document.^shipping AS shipping_info,
_full_document.items AS items
FROM t1 FINAL
WHERE _peerdb_is_deleted = 0;
Expand All @@ -304,7 +308,7 @@ SELECT
customer_id,
sum(total_amount)
FROM flattened_t1
WHERE shipping_city = 'Seattle'
WHERE shipping_info.city = 'Seattle'
GROUP BY customer_id
ORDER BY customer_id DESC
LIMIT 10;
Expand Down