Delta Lake docs (#313)

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* Update index.mdx

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---------

Co-authored-by: Prashanth Rao <[email protected]>
Co-authored-by: prrao87 <[email protected]>

src/content/docs/extensions/delta.mdx

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+---
+title: "Delta Lake"
+---
+
+import { Tabs, TabItem } from '@astrojs/starlight/components';
+
+## Usage
+
+The `delta` extension adds support for scanning/copying from the [`Delta Lake open-source storage format`](https://delta.io/). Using this extension, you can
+interact with Delta tables using [`LOAD FROM`](/cypher/query-clauses/load-from),
+[`COPY FROM`](/import/copy-from-query-results), similar to how you would
+with CSV files.
+
+The Delta functionality is not available by default, so you would first need to install the `DELTA`
+extension by running the following commands:
+
+```sql
+INSTALL DELTA;
+LOAD EXTENSION DELTA;
+```
+
+### Example dataset
+
+Let's look at an example dataset to demonstrate how the Delta extension can be used.
+Firstly, let's create a Delta table containing student information using Python and save the Delta table in the `'/tmp/student'` directory:
+Before running the script, make sure the `deltalake` Python package is properly installed (we will also use Pandas).
+```shell
+pip install deltalake pandas
+```
+
+```python
+# create_delta_table.py
+import pandas as pd
+from deltalake import DeltaTable, write_deltalake
+
+student = {
+    "name": ["Alice", "Bob", "Carol"],
+    "ID": [0, 3, 7]
+}
+
+write_deltalake(f"/tmp/student", pd.DataFrame.from_dict(student))
+```
+
+In the following sections, we will first scan the Delta table to query its contents in Cypher, and
+then proceed to copy the data and construct a node table.
+
+### Scan the Delta table
+`LOAD FROM` is a Cypher clause that scans a file or object element by element, but doesn’t actually
+move the data into a Kùzu table.
+
+To scan the Delta table created above, you can do the following:
+
+```cypher
+LOAD FROM '/tmp/student' (file_format='delta') RETURN *;
+```
+```
+┌────────┬───────┐
+│ name   │ ID    │
+│ STRING │ INT64 │
+├────────┼───────┤
+│ Alice  │ 0     │
+│ Bob    │ 3     │
+│ Carol  │ 7     │
+└────────┴───────┘
+```
+:::note[Note]
+Note: The `file_format` parameter is used to explicitly specify the file format of the given file instead of letting Kùzu autodetect the file format at runtime.
+When scanning from the Delta table, `file_format` option must be provided since Kùzu is not capable of autodetecting Delta tables.
+:::
+
+### Copy the Delta table into a node table
+You can then use a `COPY FROM` statement to directly copy the contents of the Delta table into a Kùzu node table.
+
+```cypher
+CREATE NODE TABLE student (name STRING, ID INT64, PRIMARY KEY(ID));
+COPY student FROM '/tmp/student' (file_format='delta')
+```
+
+Just like above in `LOAD FROM`, the `file_format` parameter is mandatory when specifying the `COPY FROM` clause as well.
+
+```cypher
+// First, create the node table
+CREATE NODE TABLE student (name STRING, ID INT64, PRIMARY KEY(ID));
+```
+```
+┌─────────────────────────────────┐
+│ result                          │
+│ STRING                          │
+├─────────────────────────────────┤
+│ Table student has been created. │
+└─────────────────────────────────┘
+```
+```cypher
+COPY student FROM '/tmp/student' (file_format='delta');
+```
+```
+┌─────────────────────────────────────────────────┐
+│ result                                          │
+│ STRING                                          │
+├─────────────────────────────────────────────────┤
+│ 3 tuples have been copied to the student table. │
+└─────────────────────────────────────────────────┘
+```
+
+### Access Delta tables hosted on S3
+Kùzu also supports scanning/copying a Delta table hosted on S3 in the same way as from a local file system.
+Before reading and writing from S3, you have to configure the connection using the [CALL](https://kuzudb.com/docusaurus/cypher/configuration) statement.
+
+#### Supported options
+
+| Option name | Description |
+|----------|----------|
+| `s3_access_key_id` | S3 access key id |
+| `s3_secret_access_key` | S3 secret access key |
+| `s3_endpoint` | S3 endpoint |
+| `s3_url_style` | Uses [S3 url style](https://docs.aws.amazon.com/AmazonS3/latest/userguide/VirtualHosting.html) (should either be vhost or path) |
+| `s3_region` | S3 region |
+
+#### Requirements on the S3 server API
+
+| Feature | Required S3 API features |
+|----------|----------|
+| Public file reads | HTTP Range request |
+| Private file reads | Secret key authentication|
+
+#### Scan Delta table from S3
+Reading or scanning a Delta table that's on S3 is as simple as reading from regular files:
+
+```sql
+LOAD FROM 's3://kuzu-sample/sample-delta' (file_format='delta')
+RETURN *
+```
+
+#### Copy Delta table hosted on S3 into a local node table
+
+Copying from Delta tables on S3 is also as simple as copying from regular files:
+
+```cypher
+CREATE NODE TABLE student (name STRING, ID INT64, PRIMARY KEY(ID));
+COPY student FROM 's3://kuzu-sample/student-delta' (file_format='delta')
+```
+
+### Limitations
+
+When using the Delta Lake extension in Kùzu, keep the following limitations in mind.
+
+- Writing (i.e., exporting to) Delta files is currently not supported.
+- We currently do not support scanning/copying nested data (i.e., of type `STRUCT`) in the Delta table columns.