Searching Nested Child Documents

This section exposes potential techniques which can be used for searching deeply nested documents, showcasing how more complex queries can be constructed using some of Solr’s query parsers and document transformers.

These features require _root_ and _nest_path_ to be declared in the schema. Please refer to Indexing Nested Documents for details about schema and index configuration.

This section does not demonstrate faceting on nested documents. For nested document faceting, please refer to the Block Join Facet Counts section.

Query Examples

For the upcoming examples, we’ll assume an index containing the same documents covered in Indexing Nested Documents:

[{ "id": "P11!prod",
   "name_s": "Swingline Stapler",
   "description_t": "The Cadillac of office staplers ...",
   "skus": [ { "id": "P11!S21",
               "color_s": "RED",
               "price_i": 42,
               "manuals": [ { "id": "P11!D41",
                              "name_s": "Red Swingline Brochure",
                              "pages_i":1,
                              "content_t": "..."
                            } ]
             },
             { "id": "P11!S31",
               "color_s": "BLACK",
               "price_i": 3
             } ],
   "manuals": [ { "id": "P11!D51",
                  "name_s": "Quick Reference Guide",
                  "pages_i":1,
                  "content_t": "How to use your stapler ..."
                },
                { "id": "P11!D61",
                  "name_s": "Warranty Details",
                  "pages_i":42,
                  "content_t": "... lifetime guarantee ..."
                } ]
 },
 { "id": "P22!prod",
   "name_s": "Mont Blanc Fountain Pen",
   "description_t": "A Premium Writing Instrument ...",
   "skus": [ { "id": "P22!S22",
               "color_s": "RED",
               "price_i": 89,
               "manuals": [ { "id": "P22!D42",
                              "name_s": "Red Mont Blanc Brochure",
                              "pages_i":1,
                              "content_t": "..."
                            } ]
             },
             { "id": "P22!S32",
               "color_s": "BLACK",
               "price_i": 67
             } ],
   "manuals": [ { "id": "P22!D52",
                  "name_s": "How To Use A Pen",
                  "pages_i":42,
                  "content_t": "Start by removing the cap ..."
                } ]
 } ]

Child Doc Transformer

By default, documents that match a query do not include any of their nested children in the response. The [child] Doc Transformer Can be used enrich query results with the documents' descendants.

For a detailed explanation of this transformer, and specifics on its syntax & limitations, please refer to the section [child - ChildDocTransformerFactory].

A simple query matching all documents with a description that includes "staplers":

$ curl 'http://localhost:8983/solr/gettingstarted/select?omitHeader=true&q=description_t:staplers'
{
  "response":{"numFound":1,"start":0,"maxScore":0.30136836,"numFoundExact":true,"docs":[
      {
        "id":"P11!prod",
        "name_s":"Swingline Stapler",
        "description_t":"The Cadillac of office staplers ...",
        "_version_":1672933224035123200}]
  }}

The same query with the addition of the [child] transformer is shown below. Note that the numFound has not changed, we are still matching the same set of documents, but when returning those documents the nested children are also returned as pseudo-fields.

$ curl 'http://localhost:8983/solr/gettingstarted/select?omitHeader=true&q=description_t:staplers&fl=*,[child]'
{
  "response":{"numFound":1,"start":0,"maxScore":0.30136836,"numFoundExact":true,"docs":[
      {
        "id":"P11!prod",
        "name_s":"Swingline Stapler",
        "description_t":"The Cadillac of office staplers ...",
        "_version_":1672933224035123200,
        "skus":[
          {
            "id":"P11!S21",
            "color_s":"RED",
            "price_i":42,
            "_version_":1672933224035123200,
            "manuals":[
              {
                "id":"P11!D41",
                "name_s":"Red Swingline Brochure",
                "pages_i":1,
                "content_t":"...",
                "_version_":1672933224035123200}]},

          {
            "id":"P11!S31",
            "color_s":"BLACK",
            "price_i":3,
            "_version_":1672933224035123200}],
        "manuals":[
          {
            "id":"P11!D51",
            "name_s":"Quick Reference Guide",
            "pages_i":1,
            "content_t":"How to use your stapler ...",
            "_version_":1672933224035123200},

          {
            "id":"P11!D61",
            "name_s":"Warranty Details",
            "pages_i":42,
            "content_t":"... lifetime guarantee ...",
            "_version_":1672933224035123200}]}]
  }}

Child Query Parser

The {!child} query parser can be used to search for the descendent documents of parent documents matching a wrapped query. For a detailed explanation of this parser, see the section Block Join Children Query Parser.

Let’s consider again the description_t:staplers query used above — if we wrap that query in a {!child} query parser with parentPath="/" then instead of "matching" & returning the product level documents, we instead match all of the descendent child documents of the original query:

$ curl 'http://localhost:8983/solr/gettingstarted/select' -d 'omitHeader=true' --data-urlencode 'q={!child parentPath="/"}description_t:staplers'
{
  "response":{"numFound":5,"start":0,"maxScore":0.30136836,"numFoundExact":true,"docs":[
      {
        "id":"P11!D41",
        "name_s":"Red Swingline Brochure",
        "pages_i":1,
        "content_t":"...",
        "_version_":1672933224035123200},
      {
        "id":"P11!S21",
        "color_s":"RED",
        "price_i":42,
        "_version_":1672933224035123200},
      {
        "id":"P11!S31",
        "color_s":"BLACK",
        "price_i":3,
        "_version_":1672933224035123200},
      {
        "id":"P11!D51",
        "name_s":"Quick Reference Guide",
        "pages_i":1,
        "content_t":"How to use your stapler ...",
        "_version_":1672933224035123200},
      {
        "id":"P11!D61",
        "name_s":"Warranty Details",
        "pages_i":42,
        "content_t":"... lifetime guarantee ...",
        "_version_":1672933224035123200}]
  }}

In this example parentPath="/" indicates we want to consider all root-level documents as the set of possible parents.

By changing the parentPath to a specific nest_path level, we can narrow down the list of children we return. In the query below, we search for all children of skus with a price_i less then 50:

$ curl 'http://localhost:8983/solr/gettingstarted/select' -d 'omitHeader=true' --data-urlencode 'q={!child parentPath="/skus"}price_i:[* TO 50]'
{
  "response":{"numFound":1,"start":0,"maxScore":1.0,"numFoundExact":true,"docs":[
      {
        "id":"P11!D41",
        "name_s":"Red Swingline Brochure",
        "pages_i":1,
        "content_t":"...",
        "_version_":1675662666752851968}]
  }}

Parent Query Parser

The inverse of the {!child} query parser is the {!parent} query parser, which lets you search for the ancestor documents of some child documents matching a wrapped query. For a detailed explanation of this parser, see the section Block Join Parent Query Parser.

Let’s first consider this example of searching for all "manual" type documents that have exactly 1 page:

$ curl 'http://localhost:8983/solr/gettingstarted/select?omitHeader=true&q=pages_i:1'
{
  "response":{"numFound":3,"start":0,"maxScore":1.0,"numFoundExact":true,"docs":[
      {
        "id":"P11!D41",
        "name_s":"Red Swingline Brochure",
        "pages_i":1,
        "content_t":"...",
        "_version_":1676585794196733952},
      {
        "id":"P11!D51",
        "name_s":"Quick Reference Guide",
        "pages_i":1,
        "content_t":"How to use your stapler ...",
        "_version_":1676585794196733952},
      {
        "id":"P22!D42",
        "name_s":"Red Mont Blanc Brochure",
        "pages_i":1,
        "content_t":"...",
        "_version_":1676585794347728896}]
  }}

We can wrap that query in a {!parent} query with parentPath="/" to return the details of all root-level products that are ancestors of these manuals:

$ curl 'http://localhost:8983/solr/gettingstarted/select' -d 'omitHeader=true' --data-urlencode 'q={!parent parentPath="/"}pages_i:1'
{
  "response":{"numFound":2,"start":0,"maxScore":1.4E-45,"numFoundExact":true,"docs":[
      {
        "id":"P11!prod",
        "name_s":"Swingline Stapler",
        "description_t":"The Cadillac of office staplers ...",
        "_version_":1676585794196733952},
      {
        "id":"P22!prod",
        "name_s":"Mont Blanc Fountain Pen",
        "description_t":"A Premium Writing Instrument ...",
        "_version_":1676585794347728896}]
  }}

In this example parentPath="/" indicates we want root-level documents to be the parents.

By changing parentPath to a specific path, we can change the type of ancestors we return. In the query below, we search for the skus that are the ancestors of manuals with exactly 1 page. Adding childPath="manuals" constrains the child query to only docs nested at /skus/manuals, preventing pages from other child types from matching:

$ curl 'http://localhost:8983/solr/gettingstarted/select' -d 'omitHeader=true' --data-urlencode 'q={!parent parentPath="/skus" childPath="manuals"}pages_i:1'
{
  "response":{"numFound":2,"start":0,"maxScore":1.4E-45,"numFoundExact":true,"docs":[
      {
        "id":"P11!S21",
        "color_s":"RED",
        "price_i":42,
        "_version_":1676585794196733952},
      {
        "id":"P22!S22",
        "color_s":"RED",
        "price_i":89,
        "_version_":1676585794347728896}]
  }}

Combining Block Join Query Parsers with Child Doc Transformer

The combination of these two parsers with the [child] transformer enables seamless creation of very powerful queries.

Here for example is a query where:

the (sku) documents returned must have a color of "RED"
the (sku) documents returned must be the descendents of root level (product) documents which have:
- immediate child "manuals" documents which have:
  - "lifetime guarantee" in their content
each return (sku) document also includes any descendent (manuals) documents it has

$ curl 'http://localhost:8983/solr/gettingstarted/select' -d 'omitHeader=true' -d 'fq=color_s:RED' --data-urlencode 'q={!child parentPath="/" filters=$parent_fq}' --data-urlencode 'parent_fq={!parent parentPath="/"}content_t:"lifetime guarantee"' -d 'fl=*,[child]'
{
  "response":{"numFound":1,"start":0,"maxScore":1.4E-45,"numFoundExact":true,"docs":[
      {
        "id":"P11!S21",
        "color_s":"RED",
        "price_i":42,
        "_version_":1676585794196733952,
        "manuals":[
          {
            "id":"P11!D41",
            "name_s":"Red Swingline Brochure",
            "pages_i":1,
            "content_t":"...",
            "_version_":1676585794196733952}]}]
  }}