# Code Samples

#### Using Polybase database

To use the Polybase database you can either use the default one that the data programs team has created or you can choose to read from a different one. To use the default database you will need the following import.

```typescript

import {DB} from "@dataprograms/repdao-polybase";

```

To read from a different database you will have to add the below where `NAME_SPACE` is the name of the space you want to use.  

```typescript
import { Polybase } from "@polybase/client"
const db = new Polybase({ defaultNamespace: "NAME_SPACE" });
```

The following examples will use the default Polybase database provided. It should also be noted that results are [paginated ](https://polybase.xyz/docs/read#pagination)and the developer is responsible for paging through the results if 100 rows is not enough.

### Code Samples

#### Filtering by single column value in single collection

Example is getting one row where the provider is `f01889512` in the `filfox` collection. Currently filtering and sorting on multiple columns is not supported because you have to create an index on the columns to support multiple where statements. [see doc.](https://polybase.xyz/docs/read#collection-filters)

```typescript
import {DB, filfox} from "@dataprograms/repdao-polybase";

const provider = 'f01889512'

const doc = (await DB.collection('filfox')
    .where('provider', '==', provider)
    .limit(1).get())
    .data[0].data as filfox

console.log(`Filfox record for ${provider}: total rewards: ${doc.totalRewards}`)
```

You can however have multiple where statements on the same column name.

```typescript
import {DB, filfox} from "@dataprograms/repdao-polybase";

const doc = (await DB.collection('filfox')
    .where('provider', '>', 'f01889512')
    .where('provider', '<=', 'f01889612')
    .limit(1).get())
    .data[0].data as filfox
    console.log(doc)

console.log(`Filfox record has total rewards: ${doc.totalRewards}`)
```

#### Iterating over all the provided collections

```typescript
import {PolybaseError } from "@polybase/client"
import {DB, CollectionNames} from "@dataprograms/repdao-polybase";

for (const collectionName of CollectionNames) {
    let response
    try {
        response = await DB.collection(collectionName).limit(1).get()
        console.log(`Data for polybase collection ${collectionName}`)
        console.log(response.data[0].data)
    } catch (e: any) {
        if (e instanceof PolybaseError) {
            console.error(`Polybase error: ${e.code} ${e.message} when retrieving ${collectionName}.`)
            continue
        }
        throw e
    }
}
```

#### Sorting column to find max or min

This example finds the max `epoch` that is less than `2849899` in the `filfox` collection.

```typescript
import {DB, filfox} from "@dataprograms/repdao-polybase";

const doc = (await DB.collection('filfox')
    .where('epoch', '<', 2849899)
    .sort('epoch', 'desc')
    .limit(1).get())
    .data[0].data as filfox
    console.log(doc)

console.log(`Filfox record: ${doc.provider}`)
```

#### Using sort and limit to find the top n

This example finds the 2 largest `epoch` values that are less than `2849899` in the `filfox` collection.

```typescript
import {DB, filfox} from "@dataprograms/repdao-polybase";

const doc = (await DB.collection('filfox')
    .where('epoch', '<', 2849899)
    .sort('epoch', 'desc')
    .limit(2).get()) // 2 is n

    doc.data.forEach(e => {
        console.log(e.data as filfox )
    })
```

#### Finding rows X days ago

Each collection has a column called `date_stamp` that can be used to search for rows before, after or between given dates.

```typescript
// This example won't work with the current private key 
// in the repo because date stamp was added after 

import {PolybaseError } from "@polybase/client"
import { DB, CollectionNames} from "@dataprograms/repdao-polybase";

for (const collectionName of CollectionNames) {
    let response
    try {
        let daysToLookBack = 2 //X
        response = await DB.collection(collectionName)
            .where("date_stamp", ">=", 
                (new Date(new Date().getTime() - (daysToLookBack * 24 * 60 * 60 * 1000)))
            .toISOString().substring(0,10)).sort("date_stamp", "asc").limit(2).get();
        console.log(`Data for polybase collection ${collectionName}`)
        response.data.forEach(element => {
            console.log(element.data)
        });
    } catch (e: any) {
        if (e instanceof PolybaseError) {
            console.error(`Polybase error: ${e.code} ${e.message} when retrieving ${collectionName}.`)
            continue
        }
        throw e
    }
}
```


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