solr

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 Go to latest Published: May 12, 2019 License: MIT Imports: 7 Imported by: 38

README

Go-Solr

<WARNING>

This repo is really old, and it's the first Go I ever wrote. It's probably pretty vile (I'm sure if I looked back at it now, I'd grimace a lot). Proceed with caution...

</WARNING>

An Apache Solr library written in Go, which is my first Go project! Functionality includes:

For more information on Solr itself, please refer to Solr's wiki.

This library is released under the "do whatever you like" license.

Examples / Documentation

Example programs can be found in the examples folder here.

Creating a connection - solr.Init()

Import the solr package (it is assumed you know how to build/install it, if not, see here) and create a "connection" to your solr server by calling the solr.Init(hostname, port int) function supplying a hostname and port.

// connect to server running on localhost port 8983
s, err := solr.Init("localhost", 8983)
Performing Select Queries - solr.Select()

Select queries are performed using the solr.Select(q *Query) method, passing it a pointer to a Query type.

Here's an example:

q := solr.Query{
    Params: solr.URLParamMap{
        "q": []string{"id:31"},
        "facet.field": []string{"some_field", "some_other_field"},
        "facet": "true",
    },
    Rows: 10,
    Sort: "title ASC",
}

Here we have defined a set of URL parameters - q, facet.field, facet, rows and sort using the solr.Query{} struct. Under the hood this would work out as the following Solr query string:

GET http://localhost:8983/solr/select?q=id:31&facet.field=some_field&facet.field=some_other_field&facet=true

Notice that facet_field, like q, is an array of strings and appears multiple times in the resulting query string (shown above)

Performing a query using our solr.Query() is simple and shown below

res, err := s.Select(&q)
if err != nil {
  fmt.Println(err)
}

// ...

A pointer to q is passed to s.Select(), and returned is a pointer to a SelectResponse (res) and an error (err) if an error occurred.

Iterating over the results is shown later in this document.

Performing 'Raw' Select Queries - solr.SelectRaw()

rsty/solr supports raw queries where you can specify your exact query in string form. This is useful for specifying complex queries where a Query type would be cumbersome. Raw queries are performed as follows:

q := "q={!func}add($v1,$v2)&v1=sqrt(popularity)&v2=100.0" // a solr query
res, err := s.SelectRaw(q)
if err != nil {
    // handle error here
}
// ...

In other words, under the hood the following query will have been performed:

GET http://localhost:8983/solr/select?q={!func}add($v1,$v2)&v1=sqrt(popularity)&v2=100.0

As with solr.Select(), solr.SelectRaw() returns a pointer to a SelectResponse and an error, err.

Responses - SelectResponse type

Responses to select queries (solr.Select() and solr.RawSelect()) come in the form of pointers to SelectResponse types. A SelectResponse wraps a Solr response with a convenient interface. The following few paragraphs and sections describe the various parts of a SelectResponse object

SelectResponse type

A pointer to a SelectResponse and an error are returned from calls to solr.Select() and solr.SelectRaw(). A SelectResponse mimics a Solr response and therefore has the following attributes:

  • Results - a pointer to a DocumentCollection (more on this later) which contains the documents returned by Solr
  • Status - query status indicator as returned by Solr
  • QTime - QTime value as returned by Solr

More information on Status and QTime can be found here.

DocumentCollection object

A DocumentCollection wraps up a set of Documents providing a convenient interface to them.

DocumentCollection supports the following methods:

  • Len() int - returns the length (int) of the Documents returned
  • Get(i int) *Document - returns a pointer to the document at position i within the Collection

DocumentCollection has the following properties:

  • NumFound - the total number of results solr matched to your query (irrespective of the amount returned)
  • Facets - an array of Facet objects
  • NumFacets - the number of facet fields returned (if any)
Document object

Documents implement the following methods:

  • Field(field_name string) interface{} - returns the value of the field, specified by field_name

Faceting

Facet object

If your select query specifies facets, facets will be found under Response.Results.Facets which is an array of Facets. A Facet has the following attributes

  • Name - the name of the facet (field) as returned by Solr
  • Counts - an array of FacetCounts, the corresponding value counts for the field.
FacetCount object

A FacetCount has the following attributes

  • Value - the facet field value
  • Count - the count (int) for the field value
Faceting example

Below is an example showing an iteration over a collection of Facets

// q is assumed to have been set up

// perform the query
res, err := s.Query(&q)

// handle error, err, here

results := res.Results
for i := 0; i < results.NumFacets; i++ {
    facet := results.Facets[i]
    fmt.Println("Facet:", facet.Name)
    k := len(facet.Counts)
    for j := 0; j < k; j++ {
        fmt.Println(facet.Counts[j].Value, "=>", facet.Counts[j].Count)
    }
    fmt.Println("")
}

This might output the following:

Facets
------
Facet: category
cameras => 1

Facet: type
digital_slr => 10
compact => 2

Update Queries - solr.Update()

Update queries are used to add, replace or delete documents in Solr's index. Please see the Solr Wiki for more information. Go-Solr uses JSON for update queries, not XML. Solr3.1 will need to be configured to support JSON for update messages, Solr 4.0+ supports JSON natively via /update.

Creating an Update query - example

solr.Update(document map[string]interface{}, commit bool) takes two arguments, an "update document" and a commit flag (boolean) which specifies whether or not a commit should be performed at the same time as the update is performed. An example may look like the following

q, err := solr.Update(document, true);
if err != nil {
    // ...
}

An update document must be of type map[string]interface{}, and may look like the following:

doc := map[string]interface {}{
    "add":[]interface {}{
        map[string]interface {}{"id": 22, "title": "abc"},
        map[string]interface {}{"id": 23, "title": "def"},
        map[string]interface {}{"id": 24, "title": "def"},
    },
}

... which is equivalent to the following JSON:

{"add": [{"id": 22, "title": "abc"}, {"id": 23, "title": "def"}, {"id": 24, "title": "def"}]}

... which is an Update which adds (or replaces) 3 documents in a fictional Solr index.

You can define any type of document to send off to Solr in an update. Support will be added later to allow raw JSON strings to be used in Updates.

solr.Update() returns an UpdateResponse and an error. UpdateResponse has a Success (bool) property.

Documentation

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func BytesToJSON 

func BytesToJSON(b *[]byte) (*interface{}, error)

* Decodes a json formatted []byte into an interface{} type

func EncodeURLParamMap 

func EncodeURLParamMap(m *URLParamMap) string

* Returns a URLEncoded version of a Param Map * E.g., ParamMap[foo:bar omg:wtf] => "foo=bar&omg=wtf" * TODO: This isn't exactly safe and there's probably a library pkg to do this already...

func HTTPGet 

func HTTPGet(httpUrl string) ([]byte, error)

* Performs a GET request to the given url * Returns a []byte containing the response body

func HTTPPost 

func HTTPPost(url string, headers [][]string, payload *[]byte) ([]byte, error)

* Performs a HTTP Post request. Takes: * * A url * * Headers, in the format [][]string{} (e.g., [[key, val], [key, val], ...]) * * A payload (post request body) which can be nil * * Returns the body of the response and an error if necessary

func JSONToBytes 

func JSONToBytes(m map[string]interface{}) (*[]byte, error)

* Encodes a map[string]interface{} to bytes and returns * a pointer to said bytes

func SolrSelectString 

func SolrSelectString(c *Connection, q string, handlerName string) string

* Generates a Solr query string from a connection, query string and handler name

func SolrUpdateString 

func SolrUpdateString(c *Connection, commit bool) string

* Generates a Solr update query string. Adds ?commit=true * if commit arg is true.

Types

type Connection 

type Connection struct {
	URL     string
	Version []int
}

* Represents a "connection"; actually just a host and port * (and probably at some point a Solr Core name)

func Init 

func Init(host string, port int, core string) (*Connection, error)

* Inits a new Connection to a Solr instance * Note: this doesn't actually hold a connection, its just * a container for the URL. * This creates a URL with the pattern http://{host}:{port}/solr/{core} * If you want to create a connection with another pattern just create * the struct directly i.e. conn := &Connection{myCustomURL}.

func (*Connection) CustomSelect 

func (c *Connection) CustomSelect(q *Query, handlerName string) (*SelectResponse, error)

* Performs a Select query given a Query and handlerName

func (*Connection) CustomSelectRaw 

func (c *Connection) CustomSelectRaw(q string, handlerName string) (*SelectResponse, error)

* Performs a raw Select query given a raw query string and handlerName

func (*Connection) Select 

func (c *Connection) Select(q *Query) (*SelectResponse, error)

* Performs a Select query given a Query

func (*Connection) SelectRaw 

func (c *Connection) SelectRaw(q string) (*SelectResponse, error)

* Performs a raw Select query given a raw query string

func (*Connection) Update 

func (c *Connection) Update(m map[string]interface{}, commit bool) (*UpdateResponse, error)

* Performs a Solr Update query against a given update document * specified in a map[string]interface{} type * NOTE: Requires JSON updates to be enabled, see; * http://wiki.apache.org/solr/UpdateJSON * FUTURE: Will ask for solr version details in Connection and * act appropriately

type Document 

type Document struct {
	Fields map[string]interface{}
}

* Represents a Solr document, as returned by Select queries

func (Document) Doc 

func (document Document) Doc() map[string]interface{}

* Document.Doc() returns the raw document (map)

func (Document) Field 

func (document Document) Field(field string) interface{}

* Document.Field() returns the value of the given field name in the document

type DocumentCollection 

type DocumentCollection struct {
	Facets     []Facet
	Collection []Document
	NumFacets  int // convenience...
	NumFound   int
	Start      int
}

* Represents a collection of solr documents * and various other metrics

func (*DocumentCollection) Get 

func (d *DocumentCollection) Get(i int) *Document

* DocumentCollection.Get() returns the document in the collection * at position i

func (*DocumentCollection) Len 

func (d *DocumentCollection) Len() int

* DocumentCollection.Len() returns the amount of documents * in the collection

type ErrorResponse 

type ErrorResponse struct {
	Message string
	Status  int
}

* Represents an error from Solr

func SolrErrorResponse 

func SolrErrorResponse(m map[string]interface{}) (bool, *ErrorResponse)

* Determines whether a decoded response from Solr * is an error response or not. Returns a bool (true if error) * and an ErrorResponse (if the response is an error response) * otherwise nil

func (ErrorResponse) String 

func (r ErrorResponse) String() string

type Facet 

type Facet struct {
	Name   string       // accepts_4x4s
	Counts []FacetCount // a set of values
}

* Represents a Facet with a name and count

type FacetCount 

type FacetCount struct {
	Value string
	Count int
}

* Represents a FacetCount for a Facet

type Query 

type Query struct {
	Params     URLParamMap
	Rows       int
	Start      int
	Sort       string
	DefType    string
	Debug      bool
	OmitHeader bool
}

* Query represents a query with various params

func (*Query) String 

func (q *Query) String() string

* Query.String() returns the Query in solr query string format

type SelectResponse 

type SelectResponse struct {
	Results *DocumentCollection
	Status  int
	QTime   int
}

* Represents a Solr response

func BuildResponse 

func BuildResponse(j *interface{}) (*SelectResponse, error)

* Takes a JSON formatted Solr response (interface{}, not []byte) * And returns a *Response

func SelectResponseFromHTTPResponse 

func SelectResponseFromHTTPResponse(b []byte) (*SelectResponse, error)

* Decodes a HTTP (Solr) response and returns a Response

func (SelectResponse) String 

func (r SelectResponse) String() string

type URLParamMap 

type URLParamMap map[string][]string

* Holds URL parameters

type UpdateResponse 

type UpdateResponse struct {
	Success bool
}

func (UpdateResponse) String 

func (r UpdateResponse) String() string

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