Scott Chamberlain

## DBI

What is DBI? [DBI](https://cran.r-project.org/web/packages/DBI/) is an R
package. It defines an interface to relational database management
systems (R/DBMS) that other R packages build upon to interact with a
specific relational database, such as [SQLite](https://sqlite.org/) or
[PostgreSQL](https://www.postgresql.org/).

## NoSQL

[NoSQL databases](https://nosql-database.org/) are a very broad class of
database that can include document databases such as CouchDB and
MongoDB, key-value stores such as Redis, and more. They are generally
not row-column relational stores though, though can include that. NoSQL
is often thought of now as "not only SQL".

You can imagine how it is relatively straight-forward to create a common
interace to row-column oriented databases, and DBI is great for that.

However, a common interface to NoSQL datbases is a bit harder to wrap
your head around for various reasons. One of the most obvious of which
is that they don't share a fundamental data structure like R/DMBS do.

## A sort of DBI for NoSQL

[nodbi](https://github.com/ropensci/nodbi) (the `no` for "N" and "O" in
"NoSQL") was started nearly 3 years ago during the [2015 rOpenSci
Unconference](https://github.com/ropensci/unconf15) on [26
March](https://github.com/ropensci/nodbi/commits/29340320b28f13e942ae177886d3d6b87366c4c2)
together with [Rich FitzJohn](https://github.com/richfitz) and [Jeroen
Ooms](https://github.com/jeroen). We've worked on it here and there, but
it hasn't seen any commits in nearly a year.

Given the success of
[dplyr](https://cran.r-project.org/web/packages/dplyr/) it goes to
reason that something that can abstract away the details for NoSQL
databases - for a subset of the most common operations - could prove to
be very useful.

nodbi takes a different approach than DBI (thus the "sort of" in this
section title) in that instead of package X for database Y importing DBI
and extending its methods, nodbi provides the connection objects to
various databases, and a set of common methods for interacting with
those databases. Whereas DBI doesn't import or depend in any way on
packages for individual databases, nodbi has packages for individual
databases in Suggests. That is to say, nodbi can be installed and loaded
without any specific database package, but to use any one database
(e.g., Mongo) you need to install the package for that database (i.e.,
[mongolite](https://cran.r-project.org/web/packages/mongolite/)).
Because database packages in nodbi are in Suggests, you can pick and
choose the packages you want to have installed - and forget about the
others.

Check out the package [on GitHub](https://github.com/ropensci/nodbi).

## data.frame's

Thus far, we've built nodbi around data.frame's. That is, we're focusing
on the data.frame use case as it's very common that R users are dealing
solely with data.frame's in their analysis pipelines.

Let us know if you have a strong need for lists or vectors, etc. in
nodbi.

## supported databases

Connection functions to each database follow the pattern `src_`
following the pattern used by `dplyr`

- MongoDB: `src_mongo`
- Redis: `src_redis`
- CouchDB: `src_couchdb`
- Elasticsvearch: `src_elastic`
- Etcd: `src_etcd`

The details of connecting to different databases vary as you'd imagine,
but what's returned from `src_` functions can be passed to any of the
below methods (for the most part).

## supported methods

- create (`docdb_create`): Create an object
- get (`docdb_get`): Get an object
- delete (`docdb_delete`): Delete an object
- update (`docdb_update`): Update an object. CouchDB only for now

Operations in nodbi follow a key-value pattern. That is, an object
(read: data.frame) is stored in your choice of database with a key
(read: character string). Not every operation above needs both the key
and value - for example, deleting an object only requires the key.

Internally, a key maps differently to Redis vs. Mongo vs. CouchDB, etc.
But the point is that we're abstracting away the details so that the
user can focus on getting things done faster.

## Setup

You'll need to start up the database you want to work with if it's not
started already. Let's work with Mongo for this blog post.

Check out the [mongolite book](https://jeroen.github.io/mongolite/) for
details on installing MongoDB

Start up mongo on your cli (i.e., shell or terminal)

``` {tabindex="0"}
mongod # or sudo mongod
```

Install database packages

::: {.highlight}
``` {.chroma tabindex="0"}
install.packages(c("sofa", "etseed", "elastic", "mongolite", "redux"))
```
:::

Install nodbi

::: {.highlight}
``` {.chroma tabindex="0"}
devtools::install_github("ropensci/nodbi")
```
:::

::: {.highlight}
``` {.chroma tabindex="0"}
library(nodbi)
```
:::

## Examples

Connect to Mongo with `src_mongo`

::: {.highlight}
``` {.chroma tabindex="0"}
(src <- src_mongo(verbose = FALSE))#> MongoDB 3.6.2 (uptime: 3017s)#> URL: leothelion.local/test
```
:::

With the connection object you can access the name of the Mongo database

::: {.highlight}
``` {.chroma tabindex="0"}
src$db#> [1] "test"
```
:::

And the connection `mongolite` connection object

::: {.highlight}
``` {.chroma tabindex="0"}
src$con#> <Mongo collection> 'test' #>  $aggregate(pipeline = "{}", options = "{\"allowDiskUse\":true}", handler = NULL, pagesize = 1000) #>  $count(query = "{}") #>  $distinct(key, query = "{}") #>  $drop() #>  $export(con = stdout(), bson = FALSE) #>  $find(query = "{}", fields = "{\"_id\":0}", sort = "{}", skip = 0, limit = 0, handler = NULL, pagesize = 1000) #>  $import(con, bson = FALSE) #>  $index(add = NULL, remove = NULL) #>  $info() #>  $insert(data, pagesize = 1000, stop_on_error = TRUE, ...) #>  $iterate(query = "{}", fields = "{\"_id\":0}", sort = "{}", skip = 0, limit = 0) #>  $mapreduce(map, reduce, query = "{}", sort = "{}", limit = 0, out = NULL, scope = NULL) #>  $remove(query, just_one = FALSE) #>  $rename(name, db = NULL) #>  $replace(query, update = "{}", upsert = FALSE) #>  $update(query, update = "{\"$set\":{}}", filters = NULL, upsert = FALSE, multiple = FALSE)
```
:::

Insert a data.frame (the returned object is from `mongolite`) using
`docdb_create`

::: {.highlight}
``` {.chroma tabindex="0"}
library("ggplot2")x <- docdb_create(src = src, key = "diamonds", value = diamonds)x#> List of 5#>  $ nInserted  : num 53940#>  $ nMatched   : num 0#>  $ nRemoved   : num 0#>  $ nUpserted  : num 0#>  $ writeErrors: list()
```
:::

Get the data.frame back from Mongo using `docdb_get`

::: {.highlight}
``` {.chroma tabindex="0"}
head(docdb_get(src, "diamonds"))#>   carat       cut color clarity depth table price    x    y    z#> 1  0.23     Ideal     E     SI2  61.5    55   326 3.95 3.98 2.43#> 2  0.21   Premium     E     SI1  59.8    61   326 3.89 3.84 2.31#> 3  0.23      Good     E     VS1  56.9    65   327 4.05 4.07 2.31#> 4  0.29   Premium     I     VS2  62.4    58   334 4.20 4.23 2.63#> 5  0.31      Good     J     SI2  63.3    58   335 4.34 4.35 2.75#> 6  0.24 Very Good     J    VVS2  62.8    57   336 3.94 3.96 2.48
```
:::

Delete the object using `docdb_delete`

::: {.highlight}
``` {.chroma tabindex="0"}
docdb_delete(src, "diamonds")
```
:::

The same pattern as above can be used for any of the other database
options, except the connecting with `src_*` differs among databases.

## similar art

The one that comes closest is [storr](https://github.com/richfitz/storr)
by [Rich FitzJohn](https://github.com/richfitz) - which shares Redis in
common with nodbi as a backend. storr seems to be more focused on the
caching use case - whereas, nodbi focuses on user X has a specific
database they keep their data in and they'd like to not worry about the
details of working with that database. Perhaps the distinction isn't
really there, I'm not sure.

## Todo

- We plan to add support for more databases, let us know what you want
  supported
- We may add more operations in addition to create/get/delete/update.
  What things do you want nodbi to do?
- [Fetching partial
  data.frame's](https://github.com/ropensci/nodbi/issues/10)
- Speed ups of course, in due time
- Eventually we'll push a version to CRAN - we're hoping to get more
  users kicking the tires before that.

## Feedback!

We'd love to get some eyes on this; to sort out problems that will no
doubt arise from real world scenarios; to flesh out new use cases we
hadn't thought of, etc.

Open an issue: <https://github.com/ropensci/nodbi/issues/new>.


DBI  What is DBI? DBI is an R package. It defines an interface to relational database management systems (R/DBMS) that other R packages build upon to interact with a specific relational database, such as SQLite or PostgreSQL.NoSQL  NoSQL databases are a very broad class of database that can include document databases such as CouchDB and MongoDB, key-value stores such as Redis, and more.

Postagens de Rogue Scholar

nodbi: the NoSQL Database Connector