db_query: Query a database.

In ropensci/sofa: Connector to 'CouchDB'

Query a database.

Description

Query a database.

Usage

db_query(
  cushion,
  dbname,
  query = NULL,
  selector = NULL,
  limit = NULL,
  skip = NULL,
  sort = NULL,
  fields = NULL,
  use_index = NULL,
  r = NULL,
  bookmark = NULL,
  update = NULL,
  stable = NULL,
  stale = NULL,
  execution_stats = FALSE,
  as = "list",
  ...
)

Arguments

cushion	A Cushion object. Required.
dbname	Database name
query	(character) instead of using the other parameters, you can compose one R list or json blob here
selector	(list/json) - JSON object describing criteria used to select documents. More information provided in the section on selector syntax. See the query_tutorial in this package, and the selectors docs http://docs.couchdb.org/en/2.0.0/api/database/find.html#find-selectors
limit	(numeric) - Maximum number of results returned. Default is 25. Optional
skip	(numeric) - Skip the first 'n' results, where 'n' is the value specified. Optional
sort	(json) - JSON array following sort syntax. Optional. See http://docs.couchdb.org/en/2.0.0/api/database/find.html#find-sort For some reason, sort doesn't work often, not sure why.
fields	(json) - JSON array specifying which fields of each object should be returned. If it is omitted, the entire object is returned. More information provided in the section on filtering fields. Optional See http://docs.couchdb.org/en/2.0.0/api/database/find.html#find-filter
use_index	(json) - Instruct a query to use a specific index. Specified either as ⁠<design_document>⁠ or ⁠["<design_document>", "<index_name>"]⁠. Optional
r	(numeric) Read quorum needed for the result. This defaults to 1, in which case the document found in the index is returned. If set to a higher value, each document is read from at least that many replicas before it is returned in the results. This is likely to take more time than using only the document stored locally with the index. Optional, default: 1
bookmark	(character) A string that enables you to specify which page of results you require. Used for paging through result sets. Every query returns an opaque string under the bookmark key that can then be passed back in a query to get the next page of results. If any part of the selector query changes between requests, the results are undefined. Optional, default: NULL
update	(logical) Whether to update the index prior to returning the result. Default is true. Optional
stable	(logical) Whether or not the view results should be returned from a “stable” set of shards. Optional
stale	(character) Combination of update=FALSE and stable=TRUE options. Possible options: "ok", "FALSE" (default). Optional
execution_stats	(logical) Include execution statistics in the query response. Optional, default: FALSE
as	(character) One of list (default) or json
...	Curl args passed on to HttpClient

Value

JSON as a character string or a list (determined by the as parameter)

Examples

## Not run: 
## create a connection
user <- Sys.getenv("COUCHDB_TEST_USER")
pwd <- Sys.getenv("COUCHDB_TEST_PWD")
(x <- Cushion$new(user=user, pwd=pwd))

file <- system.file("examples/omdb.json", package = "sofa")
strs <- readLines(file)

## create a database
if ("omdb" %in% db_list(x)) {
  invisible(db_delete(x, dbname="omdb"))
}
db_create(x, dbname='omdb')

## add some documents
invisible(db_bulk_create(x, "omdb", strs))

## query all in one json blob
db_query(x, dbname = "omdb", query = '{
  "selector": {
    "_id": {
      "$gt": null
    }
  }
}')

## query with each parameter
db_query(x, dbname = "omdb",
  selector = list(`_id` = list(`$gt` = NULL)))

db_query(x, dbname = "omdb",
  selector = list(`_id` = list(`$gt` = NULL)), limit = 3)

# fields
## single field works
db_query(x, dbname = "omdb",
  selector = list(`_id` = list(`$gt` = NULL)), limit = 3,
  fields = c('_id', 'Actors', 'imdbRating'))

## as well as many fields
db_query(x, dbname = "omdb",
  selector = list(`_id` = list(`$gt` = NULL)), limit = 3,
  fields = '_id')

## other queries
db_query(x, dbname = "omdb",
  selector = list(Year = list(`$gt` = "2013")))

db_query(x, dbname = "omdb", selector = list(Rated = "R"))

db_query(x, dbname = "omdb",
  selector = list(Rated = "PG", Language = "English"))

db_query(x, dbname = "omdb", selector = list(
  `$or` = list(
    list(Director = "Jon Favreau"),
    list(Director = "Spike Lee")
  )
), fields = c("_id", "Director"))

## when selector vars are of same name, use a JSON string
## b/c R doesn't let you have a list with same name slots
db_query(x, dbname = "omdb", query = '{
  "selector": {
    "Year": {"$gte": "1990"},
    "Year": {"$lte": "2000"},
    "$not": {"Year": "1998"}
  },
  "fields": ["_id", "Year"]
}')

## regex
db_query(x, dbname = "omdb", selector = list(
  Director = list(`$regex` = "^R")
), fields = c("_id", "Director"))


## End(Not run)

ropensci/sofa documentation built on March 10, 2024, 4:26 a.m.