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title: Querying Delta Lake Tables in S3-compatible object storage
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navTitle: External Tables
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description: Access and Query data stored as Delta Lake Tablles in S3-compatible object storage using External Tables
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deepToC: true
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---
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## Overview
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External tables allow you to access and query data stored in S3-compatible object storage using SQL. You can create an external table that references data in S3-compatible object storage and query the data using standard SQL commands.
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## Prerequisites
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* An EDB Postgres AI account and a Lakehouse node.
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* An S3-compatible object storage location with data stored as Delta Lake Tables.
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* See [Bringing your own data](reference/loadingdata) for more information on how to prepare your data.
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* Credentials to access the S3-compatible object storage location, unless it is a public bucket.
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* These credentials will be stored within the database. We recommend creating a separate user with limited permissions for this purpose.
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!!! Note Regions, latency and cost
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Using an S3 bucket that isn't in the same region as your node will
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* be slow because of cross-region latencies
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* will incur AWS costs (between $0.01 and $0.02 / GB) for data transfer. Currently these egress costs are not passed through to you but we do track them and reserve the right to terminate an instance.
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!!!
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## Creating an External Storage Location
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The first step is to create an external storage location which references S3-compatible object storage where your data resides. A storage location is an object within the database which you refer to to access the data; each storage location has a name for this purpose.
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Creating a named storage location is performed with SQL by executing the `pgaa.create_storage_location` function.
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`pgaa` is the name of the extension and namespace that provides the functionality to query external storage locations.
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The `create_storage_location` function takes a name for the new storage location, and the URI of the S3-compatible object storage location as parameters.
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The function optionally can take a third parameter, `options`, which is a JSON object for specifying optional settings, detailed in the [functions reference](reference/functions#pgaacreate_storage_location).
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For example, in the options, you can specify the access key ID and secret access key for the storage location to enable access to a private bucket.
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The following example creates an external table that references a public S3-compatible object storage location:
After creating the external storage location, you can create an external table that references the data in the storage location.
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The following example creates an external table that references a Delta Lake Table in the S3-compatible object storage location:
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```sql
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CREATETABLEpublic.customer () USING PGAA WITH (pgaa.storage_location='sample-data', pgaa.path='tpch_sf_1/customer');
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```
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Note that the schema is not defined in the `CREATE TABLE` statement. The pgaa extension expects the schema to be defined in the storage location, and the schema itself is derived from the schema stored at the path specified in the `pgaa.path` option. The pgaa extension will infer the best Postgres-equivalent data types for the columns in the Delta Table.
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## Querying an External Table
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After creating the external table, you can query the data in the external table using standard SQL commands. The following example queries the external table created in the previous step:
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block storage device and will survive a restart or backup/restore cycle.
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* Only Postgres 16 is supported.
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For more notes about supported instance sizes,
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see [Reference - Supported AWS instances](./reference/#supported-aws-instances).
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For more notes about supported instance sizes,see [Reference - Supported AWS instances](./reference/instances).
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## Operating a Lakehouse node
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### Connect to the node
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You can connect to the Lakehouse node with any Postgres client, in the same way
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that you connect to any other cluster from EDB Postgres AI Cloud Service
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(formerly known as BigAnimal): navigate to the cluster detail page and copy its
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connection string.
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You can connect to the Lakehouse node with any Postgres client, in the same way that you connect to any other cluster from EDB Postgres AI Cloud Service (formerly known as BigAnimal): navigate to the cluster detail page and copy its connection string.
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For example, you might copy the `.pgpass` blob into `~/.pgpass` (making sure to
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replace `$YOUR_PASSWORD` with the password you provided when launching the
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cluster). Then you can copy the connection string and use it as an argument to
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`psql` or `pgcli`.
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For example, you might copy the `.pgpass` blob into `~/.pgpass` (making sure to replace `$YOUR_PASSWORD` with the password you provided when launching the cluster).
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Then you can copy the connection string and use it as an argument to `psql` or `pgcli`.
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In general, you should be able to connect to the database with any Postgres
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client. We expect all introspection queries to work, and if you find one that
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doesn't, then that's a bug.
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In general, you should be able to connect to the database with any Postgres client.
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We expect all introspection queries to work, and if you find one that doesn't, then that's a bug.
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### Understand the constraints
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* Every cluster uses EPAS or PGE. So expect to see boilerplate tables from those
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flavors in the installation when you connect.
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* Queryable data (like the benchmarking datasets) is stored in object storage
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as Delta Tables. Every cluster comes pre-loaded to point to a storage bucket
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with benchmarking data inside (TPC-H, TPC-DS, Clickbench) at
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scale factors 1 and 10.
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* Every cluster uses EPAS or PGE. So expect to see boilerplate tables from those flavors in the installation when you connect.
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* Queryable data (like the benchmarking datasets) is stored in object storage as Delta Tables. Every cluster comes pre-loaded to point to a storage bucket with benchmarking data inside (TPC-H, TPC-DS, Clickbench) at scale factors from 1 to 1000.
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* Only AWS is supported at the moment. Bring Your Own Account (BYOA) is not supported.
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* You can deploy a cluster in any region that is activated in
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your EDB Postgres AI Account. Each region has a bucket with a copy of the
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benchmarking data, and so when you launch a cluster, it will use the
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benchmarking data in the location closest to it.
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* The cluster is ephemeral. None of the data is stored on the hard drive,
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except for data in system tables, e.g. roles and users and grants.
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If you restart the cluster, or backup the cluster and then restore it,
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it will restore these system tables. But the data in object storage will
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* You can deploy a cluster in any region that is activated in your EDB Postgres AI Account. Each region has a bucket with a copy of the
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benchmarking data, and so when you launch a cluster, it will use the benchmarking data in the location closest to it.
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* The cluster is ephemeral. None of the data is stored on the hard drive, except for data in system tables, e.g. roles and users and grants.
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If you restart the cluster, or backup the cluster and then restore it, it will restore these system tables. But the data in object storage will
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remain untouched.
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* The cluster supports READ ONLY queries of the data in object
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storage (but it supports write queries to system tables for creating users,
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* The cluster supports READ ONLY queries of the data in object storage (but it supports write queries to system tables for creating users,
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etc.). You cannot write directly to object storage. You cannot create new tables.
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* If you want to load your own data into object storage,
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see [Reference - Bring your own data](./reference/#advanced-bring-your-own-data).
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* If you want to load your own data into object storage, see [Reference - Bring your own data](reference/loadingdata).
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## Inspect the benchmark datasets
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* 1 Billion Row Challenge
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For more details on benchmark datasets,
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see Reference - Available benchmarking datasets](./reference/#available-benchmarking-datasets).
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see Reference - Available benchmarking datasets](./reference/datasets).
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