ent/doc/website/blog/2025-02-12-rag-with-ent-atlas-pgvector.mdx

---
title: "Building RAG systems in Go with Ent, Atlas, and pgvector"
author: Rotem Tamir
authorURL: "https://github.com/rotemtam"
authorImageURL: "https://s.gravatar.com/avatar/36b3739951a27d2e37251867b7d44b1a?s=80"
authorTwitter: _rtam
image: "https://atlasgo.io/uploads/entrag.png"
---
In this blog post, we will explore how to build a [RAG](https://en.wikipedia.org/wiki/Retrieval-augmented_generation)
(Retrieval Augmented Generation) system using [Ent](https://entgo.io), [Atlas](https://atlasgo.io), and
[pgvector](https://github.com/pgvector/pgvector).

RAG is a technique that augments the power of generative models by incorporating a retrieval step. Instead of relying
solely on the model’s internal knowledge, we can retrieve relevant documents or data from an external source and use
that information to produce more accurate, context-aware responses. This approach is particularly useful when building
applications such as question-answering systems, chatbots, or any scenario where up-to-date or domain-specific knowledge
is needed.

### Setting Up our Ent schema

Let's begin our tutorial by initializing the Go module which we will be using for our project:

```bash
go mod init github.com/rotemtam/entrag # Feel free to replace the module path with your own
```

In this project we will use [Ent](/), an entity framework for Go, to define our database schema. The database will store
the documents we want to retrieve (chunked to a fixed size) and the vectors representing each chunk. Initialize the Ent
project by running the following command:

```bash
go run -mod=mod entgo.io/ent/cmd/ent new Embedding Chunk
```

This command creates placeholders for our data models. Our project should look like this:

```
├── ent
│   ├── generate.go
│   └── schema
│       ├── chunk.go
│       └── embedding.go
├── go.mod
└── go.sum
```

Next, let's define the schema for the `Chunk` model. Open the `ent/schema/chunk.go` file and define the schema as follows:

```go title="ent/schema/chunk.go"
package schema

import (
	"entgo.io/ent"
	"entgo.io/ent/schema/edge"
	"entgo.io/ent/schema/field"
)

// Chunk holds the schema definition for the Chunk entity.
type Chunk struct {
	ent.Schema
}

// Fields of the Chunk.
func (Chunk) Fields() []ent.Field {
	return []ent.Field{
		field.String("path"),
		field.Int("nchunk"),
		field.Text("data"),
	}
}

// Edges of the Chunk.
func (Chunk) Edges() []ent.Edge {
	return []ent.Edge{
		edge.To("embedding", Embedding.Type).StorageKey(edge.Column("chunk_id")).Unique(),
	}
}
```
This schema defines a `Chunk` entity with three fields: `path`, `nchunk`, and `data`. The `path` field stores the path
of the document, `nchunk` stores the chunk number, and `data` stores the chunked text data. We also define an edge to
the `Embedding` entity, which will store the vector representation of the chunk.

Before we proceed, let's install the `pgvector` package. `pgvector` is a PostgreSQL extension that provides support for
vector operations and similarity search. We will need it to store and retrieve the vector representations of our chunks.

```bash
go get github.com/pgvector/pgvector-go
```

Next, let's define the schema for the `Embedding` model. Open the `ent/schema/embedding.go` file and define the schema
as follows:

```go title="ent/schema/embedding.go"
package schema

import (
	"entgo.io/ent"
	"entgo.io/ent/dialect"
	"entgo.io/ent/dialect/entsql"
	"entgo.io/ent/schema/edge"
	"entgo.io/ent/schema/field"
	"entgo.io/ent/schema/index"
	"github.com/pgvector/pgvector-go"
)

// Embedding holds the schema definition for the Embedding entity.
type Embedding struct {
	ent.Schema
}

// Fields of the Embedding.
func (Embedding) Fields() []ent.Field {
	return []ent.Field{
		field.Other("embedding", pgvector.Vector{}).
			SchemaType(map[string]string{
				dialect.Postgres: "vector(1536)",
			}),
	}
}

// Edges of the Embedding.
func (Embedding) Edges() []ent.Edge {
	return []ent.Edge{
		edge.From("chunk", Chunk.Type).Ref("embedding").Unique().Required(),
	}
}

func (Embedding) Indexes() []ent.Index {
	return []ent.Index{
		index.Fields("embedding").
			Annotations(
				entsql.IndexType("hnsw"),
				entsql.OpClass("vector_l2_ops"),
			),
	}
}
```

This schema defines an `Embedding` entity with a single field `embedding` of type `pgvector.Vector`. The `embedding`
field stores the vector representation of the chunk. We also define an edge to the `Chunk` entity and an index on the
`embedding` field using the `hnsw` index type and `vector_l2_ops` operator class. This index will enable us to perform
efficient similarity searches on the embeddings.

Finally, let's generate the Ent code by running the following commands:

```bash
go mod tidy
go generate ./...
```

Ent will generate the necessary code for our models based on the schema definitions.

### Setting Up the database

Next, let's set up the PostgreSQL database. We will use Docker to run a PostgreSQL instance locally. As we need the
`pgvector` extension, we will use the `pgvector/pgvector:pg17` Docker image, which comes with the extension
pre-installed.

```bash
docker run --rm --name postgres -e POSTGRES_PASSWORD=pass -p 5432:5432 -d pgvector/pgvector:pg17
```

We will be using [Atlas](https://atlasgo.io), a database schema-as-code tool that integrates with Ent, to manage our
database schema. Install Atlas by running the following command:

```
curl -sSfL https://atlasgo.io/install.sh | sh
```

For other installation options, see the [Atlas installation docs](https://atlasgo.io/getting-started#installation).

As we are going to managing extensions, we need an Atlas Pro account. You can sign up for a free trial by running:

```
atlas login
```

:::note Working without a migration tool

If you would like to skip using Atlas, you can apply the required schema directly to the database
using the statements in [this file](https://github.com/rotemtam/entrag/blob/e91722c0fbe011b03dbd6b9e68415547c8b7bba4/setup.sql#L1)

:::

Now, let's create our Atlas configuration which composes the `base.pg.hcl` file with the Ent schema:

```hcl title="atlas.hcl"
data "composite_schema" "schema" {
  schema {
    url = "file://base.pg.hcl"
  }
  schema "public" {
    url = "ent://ent/schema"
  }
}

env "local" {
  url = getenv("DB_URL")
  schema {
    src = data.composite_schema.schema.url
  }
  dev = "docker://pgvector/pg17/dev"
}
```

This configuration defines a composite schema that includes the `base.pg.hcl` file and the Ent schema. We also define an
environment named `local` that uses the composite schema which we will use for local development. The `dev` field specifies
the [Dev Database](https://atlasgo.io/concepts/dev-database) URL, which is used by Atlas to normalize schemas and make
various calculations.

Next, let's apply the schema to the database by running the following command:

```bash
export DB_URL='postgresql://postgres:pass@localhost:5432/postgres?sslmode=disable'
atlas schema apply --env local
```
Atlas will load the desired state of the database from our configuration, compare it to the current state of the database,
and create a migration plan to bring the database to the desired state:

```
Planning migration statements (5 in total):

  -- create extension "vector":
    -> CREATE EXTENSION "vector" WITH SCHEMA "public" VERSION "0.8.0";
  -- create "chunks" table:
    -> CREATE TABLE "public"."chunks" (
         "id" bigint NOT NULL GENERATED BY DEFAULT AS IDENTITY,
         "path" character varying NOT NULL,
         "nchunk" bigint NOT NULL,
         "data" text NOT NULL,
         PRIMARY KEY ("id")
       );
  -- create "embeddings" table:
    -> CREATE TABLE "public"."embeddings" (
         "id" bigint NOT NULL GENERATED BY DEFAULT AS IDENTITY,
         "embedding" public.vector(1536) NOT NULL,
         "chunk_id" bigint NOT NULL,
         PRIMARY KEY ("id"),
         CONSTRAINT "embeddings_chunks_embedding" FOREIGN KEY ("chunk_id") REFERENCES "public"."chunks" ("id") ON UPDATE NO ACTION ON DELETE NO ACTION
       );
  -- create index "embedding_embedding" to table: "embeddings":
    -> CREATE INDEX "embedding_embedding" ON "public"."embeddings" USING hnsw ("embedding" vector_l2_ops);
  -- create index "embeddings_chunk_id_key" to table: "embeddings":
    -> CREATE UNIQUE INDEX "embeddings_chunk_id_key" ON "public"."embeddings" ("chunk_id");

-------------------------------------------

Analyzing planned statements (5 in total):

  -- non-optimal columns alignment:
    -- L4: Table "chunks" has 8 redundant bytes of padding per row. To reduce disk space,
       the optimal order of the columns is as follows: "id", "nchunk", "path",
       "data" https://atlasgo.io/lint/analyzers#PG110
  -- ok (370.25µs)

  -------------------------
  -- 114.306667ms
  -- 5 schema changes
  -- 1 diagnostic

-------------------------------------------

? Approve or abort the plan:
  ▸ Approve and apply
    Abort
```

In addition to planning the change, Atlas will also provide diagnostics and suggestions for optimizing the schema. In this
case it suggests reordering the columns in the `chunks` table to reduce disk space. As we are not concerned with disk space
in this tutorial, we can proceed with the migration by selecting `Approve and apply`.

Finally, we can verify that our schema was applied successfully, we can re-run the `atlas schema apply` command. Atlas
will output:

```bash
Schema is synced, no changes to be made
```

### Scaffolding the CLI

Now that our database schema is set up, let's scaffold our CLI application. For this tutorial, we will be using
the [`alecthomas/kong`](https://github.com/alecthomas/kong) library to build a small app that can load, index
and query the documents in our database.

First, install the `kong` library:

```bash
go get github.com/alecthomas/kong
```

Next, create a new file named `cmd/entrag/main.go` and define the CLI application as follows:

```go title="cmd/entrag/main.go"
package main

import (
	"fmt"
	"os"

	"github.com/alecthomas/kong"
)

// CLI holds global options and subcommands.
type CLI struct {
	// DBURL is read from the environment variable DB_URL.
	DBURL     string `kong:"env='DB_URL',help='Database URL for the application.'"`
	OpenAIKey string `kong:"env='OPENAI_KEY',help='OpenAI API key for the application.'"`

	// Subcommands
	Load  *LoadCmd  `kong:"cmd,help='Load command that accepts a path.'"`
	Index *IndexCmd `kong:"cmd,help='Create embeddings for any chunks that do not have one.'"`
	Ask   *AskCmd   `kong:"cmd,help='Ask a question about the indexed documents'"`
}

func main() {
	var cli CLI
	app := kong.Parse(&cli,
		kong.Name("entrag"),
		kong.Description("Ask questions about markdown files."),
		kong.UsageOnError(),
	)
	if err := app.Run(&cli); err != nil {
		fmt.Fprintf(os.Stderr, "Error: %s\n", err)
		os.Exit(1)
	}
}
```

Create an additional file named `cmd/entrag/rag.go` with the following content:

```go title="cmd/entrag/rag.go"
package main

type (
	// LoadCmd loads the markdown files into the database.
	LoadCmd struct {
		Path string `help:"path to dir with markdown files" type:"existingdir" required:""`
	}
	// IndexCmd creates the embedding index on the database.
	IndexCmd struct {
	}
	// AskCmd is another leaf command.
	AskCmd struct {
		// Text is the positional argument for the ask command.
		Text string `kong:"arg,required,help='Text for the ask command.'"`
	}
)
```

Verify our scaffolded CLI application works by running:

```bash
go run ./cmd/entrag --help
```

If everything is set up correctly, you should see the help output for the CLI application:

```
Usage: entrag <command> [flags]

Ask questions about markdown files.

Flags:
  -h, --help                  Show context-sensitive help.
      --dburl=STRING          Database URL for the application ($DB_URL).
      --open-ai-key=STRING    OpenAI API key for the application ($OPENAI_KEY).

Commands:
  load --path=STRING [flags]
    Load command that accepts a path.

  index [flags]
    Create embeddings for any chunks that do not have one.

  ask <text> [flags]
    Ask a question about the indexed documents

Run "entrag <command> --help" for more information on a command.
```

### Load the documents into the database

Next, we need some markdown files to load into the database. Create a directory named `data` and add some markdown files
to it. For this example, I downloaded the [`ent/ent`](https://github.com/ent/ent) repository and used the `docs` directory
as the source of markdown files.

Now, let's implement the `LoadCmd` command to load the markdown files into the database. Open the `cmd/entrag/rag.go` file
and add the following code:

```go title="cmd/entrag/rag.go"
const (
	tokenEncoding = "cl100k_base"
	chunkSize     = 1000
)

// Run is the method called when the "load" command is executed.
func (cmd *LoadCmd) Run(ctx *CLI) error {
	client, err := ctx.entClient()
	if err != nil {
		return fmt.Errorf("failed opening connection to postgres: %w", err)
	}
	tokTotal := 0
	return filepath.WalkDir(ctx.Load.Path, func(path string, d fs.DirEntry, err error) error {
		if filepath.Ext(path) == ".mdx" || filepath.Ext(path) == ".md" {
			chunks := breakToChunks(path)
			for i, chunk := range chunks {
				tokTotal += len(chunk)
				client.Chunk.Create().
					SetData(chunk).
					SetPath(path).
					SetNchunk(i).
					SaveX(context.Background())
			}
		}
		return nil
	})
}

func (c *CLI) entClient() (*ent.Client, error) {
	return ent.Open("postgres", c.DBURL)
}
```

This code defines the `Run` method for the `LoadCmd` command. The method reads the markdown files from the specified
path, breaks them into chunks of 1000 tokens each, and saves them to the database. We use the `entClient` method to
create a new Ent client using the database URL specified in the CLI options.

For the implementation of `breakToChunks`, see the [full code](https://github.com/rotemtam/entrag/blob/93291e0c8479ecabd5f2a2e49fbaa8c49f995e70/cmd/entrag/rag.go#L157)
in the [`entrag` repository](https://github.com/rotemtam/entrag), which is based almost entirely on
[Eli Bendersky's intro to RAG in Go](https://eli.thegreenplace.net/2023/retrieval-augmented-generation-in-go/).

Finally, let's run the `load` command to load the markdown files into the database:

```bash
go run ./cmd/entrag load --path=data
```

After the command completes, you should see the chunks loaded into the database. To verify run:

```bash
docker exec -it postgres psql -U postgres -d postgres -c "SELECT COUNT(*) FROM chunks;"
```

You should see something similar to:

```
  count
-------
   276
(1 row)
```

### Indexing the embeddings

Now that we have loaded the documents into the database, we need to create embeddings for each chunk. We will use the
OpenAI API to generate embeddings for the chunks. To do this, we need to install the `openai` package:

```bash
github.com/sashabaranov/go-openai
```

If you do not have an OpenAI API key, you can sign up for an account on the
[OpenAI Platform](https://platform.openai.com/signup) and [generate an API key](https://platform.openai.com/api-keys).

We will be reading this key from the environment variable `OPENAI_KEY`, so let's set it:

```bash
export OPENAI_KEY=<your OpenAI API key>
```

Next, let's implement the `IndexCmd` command to create embeddings for the chunks. Open the `cmd/entrag/rag.go` file and
add the following code:

```go title="cmd/entrag/rag.go"
// Run is the method called when the "index" command is executed.
func (cmd *IndexCmd) Run(cli *CLI) error {
	client, err := cli.entClient()
	if err != nil {
		return fmt.Errorf("failed opening connection to postgres: %w", err)
	}
	ctx := context.Background()
	chunks := client.Chunk.Query().
		Where(
			chunk.Not(
				chunk.HasEmbedding(),
			),
		).
		Order(ent.Asc(chunk.FieldID)).
		AllX(ctx)
	for _, ch := range chunks {
		log.Println("Created embedding for chunk", ch.Path, ch.Nchunk)
		embedding := getEmbedding(ch.Data)
		_, err := client.Embedding.Create().
			SetEmbedding(pgvector.NewVector(embedding)).
			SetChunk(ch).
			Save(ctx)
		if err != nil {
			return fmt.Errorf("error creating embedding: %v", err)
		}
	}
	return nil
}

// getEmbedding invokes the OpenAI embedding API to calculate the embedding
// for the given string. It returns the embedding.
func getEmbedding(data string) []float32 {
	client := openai.NewClient(os.Getenv("OPENAI_KEY"))
	queryReq := openai.EmbeddingRequest{
		Input: []string{data},
		Model: openai.AdaEmbeddingV2,
	}
	queryResponse, err := client.CreateEmbeddings(context.Background(), queryReq)
	if err != nil {
		log.Fatalf("Error getting embedding: %v", err)
	}
	return queryResponse.Data[0].Embedding
}
```

We have defined the `Run` method for the `IndexCmd` command. The method queries the database for chunks that do not have
embeddings, generates embeddings for each chunk using the OpenAI API, and saves the embeddings to the database.

Finally, let's run the `index` command to create embeddings for the chunks:

```bash
go run ./cmd/entrag index
```

You should see logs similar to: 

```
2025/02/13 13:04:42 Created embedding for chunk /Users/home/entr/data/md/aggregate.md 0
2025/02/13 13:04:43 Created embedding for chunk /Users/home/entr/data/md/ci.mdx 0
2025/02/13 13:04:44 Created embedding for chunk /Users/home/entr/data/md/ci.mdx 1
2025/02/13 13:04:45 Created embedding for chunk /Users/home/entr/data/md/ci.mdx 2
2025/02/13 13:04:46 Created embedding for chunk /Users/home/entr/data/md/code-gen.md 0
2025/02/13 13:04:47 Created embedding for chunk /Users/home/entr/data/md/code-gen.md 1
```

### Asking questions

Now that we have loaded the documents and created embeddings for the chunks, we can implement
the `AskCmd` command to ask questions about the indexed documents. Open the `cmd/entrag/rag.go` file and add the following code:

```go title="cmd/entrag/rag.go"
// Run is the method called when the "ask" command is executed.
func (cmd *AskCmd) Run(ctx *CLI) error {
	client, err := ctx.entClient()
	if err != nil {
		return fmt.Errorf("failed opening connection to postgres: %w", err)
	}
	question := cmd.Text
	emb := getEmbedding(question)
	embVec := pgvector.NewVector(emb)
	embs := client.Embedding.
		Query().
		Order(func(s *sql.Selector) {
			s.OrderExpr(sql.ExprP("embedding <-> $1", embVec))
		}).
		WithChunk().
		Limit(5).
		AllX(context.Background())
	b := strings.Builder{}
	for _, e := range embs {
		chnk := e.Edges.Chunk
		b.WriteString(fmt.Sprintf("From file: %v\n", chnk.Path))
		b.WriteString(chnk.Data)
	}
	query := fmt.Sprintf(`Use the below information from the ent docs to answer the subsequent question.
Information:
%v

Question: %v`, b.String(), question)
	oac := openai.NewClient(ctx.OpenAIKey)
	resp, err := oac.CreateChatCompletion(
		context.Background(),
		openai.ChatCompletionRequest{
			Model: openai.GPT4o,
			Messages: []openai.ChatCompletionMessage{

				{
					Role:    openai.ChatMessageRoleUser,
					Content: query,
				},
			},
		},
	)
	if err != nil {
		return fmt.Errorf("error creating chat completion: %v", err)
	}
	choice := resp.Choices[0]
	out, err := glamour.Render(choice.Message.Content, "dark")
	fmt.Print(out)
	return nil
}
```
This is where all of the parts come together. After preparing our database with the documents and their embeddings, we
can now ask questions about them. Let's break down the `AskCmd` command:

```go
emb := getEmbedding(question)
embVec := pgvector.NewVector(emb)
embs := client.Embedding.
    Query().
    Order(func(s *sql.Selector) {
        s.OrderExpr(sql.ExprP("embedding <-> $1", embVec))
    }).
    WithChunk().
    Limit(5).
    AllX(context.Background())
```

We begin by transforming the user's question into a vector using the OpenAI API. Using this vector we would like
to find the most similar embeddings in our database. We query the database for the embeddings, order them by similarity
using `pgvector`'s `<->` operator, and limit the results to the top 5.

```go
for _, e := range embs {
		chnk := e.Edges.Chunk
		b.WriteString(fmt.Sprintf("From file: %v\n", chnk.Path))
		b.WriteString(chnk.Data)
	}
	query := fmt.Sprintf(`Use the below information from the ent docs to answer the subsequent question.
Information:
%v

Question: %v`, b.String(), question)
```
Next, we prepare the information from the top 5 chunks to be used as context for the question. We then format the
question and the context into a single string.

```go
oac := openai.NewClient(ctx.OpenAIKey)
resp, err := oac.CreateChatCompletion(
    context.Background(),
    openai.ChatCompletionRequest{
        Model: openai.GPT4o,
        Messages: []openai.ChatCompletionMessage{

            {
                Role:    openai.ChatMessageRoleUser,
                Content: query,
            },
        },
    },
)
if err != nil {
    return fmt.Errorf("error creating chat completion: %v", err)
}
choice := resp.Choices[0]
out, err := glamour.Render(choice.Message.Content, "dark")
fmt.Print(out)
```
Then, we use the OpenAI API to generate a response to the question. We pass the question and context to the API
and receive a response. We then render the response using the `glamour` package to display it in the terminal.

Before running the `ask` command, let's install the `glamour` package:

```bash
go get github.com/charmbracelet/glamour
```

Finally, let's run the `ask` command to ask a question about the indexed documents:

```bash
go run ./cmd/entrag ask "tl;dr What is Ent?"
```

And our RAG system responds:

```
  Ent is an open-source entity framework (ORM) for the Go programming language. It
  allows developers to define data models or graph-structures in Go code. Ent
  emphasizes principles such as schema as code, a statically typed and explicit
  API generated through codegen, simple queries and graph traversals, statically
  typed predicates, and storage agnosticism. It supports various databases,
  including MySQL, MariaDB, PostgreSQL, SQLite, and Gremlin-based graph databases,
  and aims to enhance productivity in Go development.
```

Amazing! We have successfully built a RAG system using Ent, Atlas, and pgvector.
We can now ask questions about the documents we loaded into the database and receive context-aware responses.

Here are some more Q&As with our nifty RAG system:

<details>
<summary>go run ./cmd/entrag ask "how to define order field in entgql"</summary>
 To define an order field in  entgql , you need to annotate a field in your  Ent
  schema using the  entgql.Annotation  with the  OrderField . Here's a step-by-
  step
  guide on how you can do it:

  1. Choose a Comparable Field: Select the field in your schema that you want to
  be orderable. This could be a text field, a timestamp, an integer, an enum, etc.
  2. Annotate the Field: Use the  entgql.OrderField  annotation on the chosen
  field. The order field name should be uppercase and match its corresponding enum
  value in the GraphQL schema.
  3. Update your Schema: Here’s an example of how to annotate your fields in the
  ent/schema :
    ```go
    func (Todo) Fields() []ent.Field {
        return []ent.Field{
            field.Text("text").
                NotEmpty().
                Annotations(
                    entgql.OrderField("TEXT"),
                ),
            field.Time("created_at").
                Default(time.Now).
                Immutable().
                Annotations(
                    entgql.OrderField("CREATED_AT"),
                ),
            field.Enum("status").
                NamedValues(
                    "InProgress", "IN_PROGRESS",
                    "Completed", "COMPLETED",
                ).
                Default("IN_PROGRESS").
                Annotations(
                    entgql.OrderField("STATUS"),
                ),
            field.Int("priority").
                Default(0).
                Annotations(
                    entgql.OrderField("PRIORITY"),
                ),
        }
    }
    ```
  4. Alternatively, Multiple Order Fields: If you want to enable ordering by
  multiple fields, you can use the  entgql.MultiOrder()  annotation:
    ```go
    func (Todo) Annotations() []schema.Annotation {
        return []schema.Annotation{
            entgql.MultiOrder(),
        }
    }
    ```

  5. Generate GraphQL Types: Ensure that the GraphQL types match this setup in
  your GraphQL schema, for example:
    ```graphql
    enum OrderDirection {
      ASC
      DESC
    }
    enum TodoOrderField {
      CREATED_AT
      PRIORITY
      STATUS
      TEXT
    }
    input TodoOrder {
      direction: OrderDirection!
      field: TodoOrderField
    }
    ```

  6. Add  orderBy  Argument to Queries: Include the  orderBy  parameter in your
  GraphQL queries to allow clients to sort items:
    ```graphql
    type Query {
      todos(
        after: Cursor
        first: Int
        before: Cursor
        last: Int
        orderBy: TodoOrder
      ): TodoConnection!
    }
    ```

  By following these steps, you ensure that your Ent-based application can support
  sorting in your GraphQL API based on various fields.


</details>

<details>
<summary> go run ./cmd/entrag ask "what's the difference between privacy rules and interceptors" </summary>
 Privacy rules and interceptors serve different purposes within the Ent
  framework, each providing distinct functionalities:

1. Privacy Rules:
* Purpose: Privacy rules are primarily concerned with enforcing access
control policies for data queries and mutations. They determine whether an
operation is allowed or denied based on predefined rules.
* Implementation: They are implemented as part of a privacy policy using the
ent.Policy  interface which includes  EvalQuery  and  EvalMutation  methods.
* Operation: Privacy rules evaluate whether specific conditions are met
before allowing or denying access to the data. They can return decisions
like  privacy.Allow ,  privacy.Deny , or  privacy.Skip  to control the flow
of evaluation.
* Use Case: Ideal for managing access control by ensuring that users can
only perform certain operations if they meet the specified criteria.
2. Interceptors:
* Purpose: Interceptors act as middleware for Ent queries, allowing
modification and customization of query behaviors. They can be used to
augment or modify queries during different stages of their lifecycle.
* Implementation: Implemented as interfaces or using the  ent.InterceptFunc
adapter. They intercept and potentially modify queries by working on the
read-path.
* Operation: Interceptors modify or enhance queries, typically without the
access control logic inherent in privacy rules. They provide hooks to
execute custom logic pre and post query execution.
* Use Case: Suitable for generic transformations or modifications to queries,
such as adding default filters, query limitations, or logging operations
without focusing on access control.


In summary, while privacy rules focus on access control, interceptors are about
managing and modifying the query execution process.
</details>

### Wrapping up

In this blog post, we explored how to build a RAG system using Ent, Atlas, and pgvector. Special thanks to
[Eli Bendersky](https://eli.thegreenplace.net/2023/retrieval-augmented-generation-in-go/) for the informative
blog post and for his great Go writing over the years!