Highlight Index Search Results
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When making a Full-Text Search query, in addition to retrieving documents that contain the searched terms, you can also request to get a list of text fragments that highlight the searched terms.
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This article provides examples of highlighting search results when querying a static-index.
Prior to reading this article, it is recommended to take a look at the Highlight search results article for general knowledge about Highlighting and for dynamic-queries examples. -
To search and get fragments with highlighted terms when querying a static-index,
the index field on which you search must be configured for highlighting. See examples below. -
In this page:
Highlight results - Map index
Configure a Map index for highlighting:
To search and get fragments with highlighted terms,
the index-field on which you search must be configured as follows:
FieldStorage.Yes
- store the field in the indexFieldIndexing.Search
- allow Full-Text searchFieldTermVector.WithPositionsAndOffsets
- store the term's position and offsets
// Define a Map index:
// ===================
public class Employees_ByNotes :
AbstractIndexCreationTask<Employee, Employees_ByNotes.IndexEntry>
{
// The IndexEntry class defines index-field 'EmployeeNotes'
public class IndexEntry
{
public string EmployeeNotes { get; set; }
}
public Employees_ByNotes()
{
// The 'Map' function defines the content of index-field 'EmployeeNotes'
Map = employees => from employee in employees
select new IndexEntry
{
EmployeeNotes = employee.Notes[0]
};
// Configure index-field 'EmployeeNotes' for highlighting:
// =======================================================
Store(x => x.EmployeeNotes, FieldStorage.Yes);
Index(x => x.EmployeeNotes, FieldIndexing.Search);
TermVector(x => x.EmployeeNotes, FieldTermVector.WithPositionsAndOffsets);
}
}
Query the index with Search
:
List<Employee> employeesResults = session
// Query the map index
.Query<Employees_ByNotes.IndexEntry, Employees_ByNotes>()
// Search for documents containing the term 'manager'
.Search(x => x.EmployeeNotes, "manager")
// Request to highlight the searched term by calling 'Highlight'
.Highlight(x => x.EmployeeNotes, 35, 2, out Highlightings managerHighlights)
.OfType<Employee>()
.ToList();
List<Employee> employeesResults = await asyncSession
// Query the map index
.Query<Employees_ByNotes.IndexEntry, Employees_ByNotes>()
// Search for documents containing the term 'manager'
.Search(x => x.EmployeeNotes, "manager")
// Request to highlight the searched term by calling 'Highlight'
.Highlight(x => x.EmployeeNotes, 35, 2, out Highlightings managerHighlights)
.OfType<Employee>()
.ToListAsync();
List<Employee> employeesResults = session.Advanced
// Query the map index
.DocumentQuery<Employees_ByNotes.IndexEntry, Employees_ByNotes>()
// Search for documents containing the term 'manager'
.Search(x => x.EmployeeNotes, "manager")
// Request to highlight the searched term by calling 'Highlight'
.Highlight(x => x.EmployeeNotes, 35, 2, out Highlightings managerHighlights)
.OfType<Employee>()
.ToList();
from index "Employees/ByNotes"
where search(EmployeeNotes, "manager")
include highlight(EmployeeNotes, 35, 2)
Query the index with Where
:
List<Employee> employeesResults = session
// Query the map index
.Query<Employees_ByNotes.IndexEntry, Employees_ByNotes>()
// Request to highlight the searched term by calling 'Highlight'
.Highlight(x => x.EmployeeNotes, 35, 2, out Highlightings managerHighlights)
// Search for documents containing the term 'manager'
.Where(x => x.EmployeeNotes.Contains("manager"))
.OfType<Employee>()
.ToList();
List<Employee> employeesResults = await asyncSession
// Query the map index
.Query<Employees_ByNotes.IndexEntry, Employees_ByNotes>()
// Request to highlight the searched term by calling 'Highlight'
.Highlight(x => x.EmployeeNotes, 35, 2, out Highlightings managerHighlights)
// Search for documents containing the term 'manager'
.Where(x => x.EmployeeNotes.Contains("manager"))
.OfType<Employee>()
.ToListAsync();
List<Employee> employeesResults = session.Advanced
// Query the map index
.DocumentQuery<Employees_ByNotes.IndexEntry, Employees_ByNotes>()
// Request to highlight the searched term by calling 'Highlight'
.Highlight(x => x.EmployeeNotes, 35, 2, out Highlightings managerHighlights)
// Search for documents containing the term 'manager'
.WhereEquals("EmployeeNotes", "manager")
.OfType<Employee>()
.ToList();
from index "Employees/ByNotes"
where EmployeeNotes == "manager"
include highlight(EmployeeNotes, 35, 2)
Process results:
// 'employeesResults' contains all Employee DOCUMENTS that contain the term 'manager'.
// 'managerHighlights' contains the text FRAGMENTS that highlight the 'manager' term.
StringBuilder builder = new StringBuilder().AppendLine("<ul>");
foreach (var employee in employeesResults)
{
// Call 'GetFragments' to get all fragments for the specified employee Id
string[] fragments = managerHighlights.GetFragments(employee.Id);
foreach (var fragment in fragments)
{
builder.AppendLine($"<li>Doc: {employee.Id}</li>");
builder.AppendLine($"<li>Fragment: {fragment}</li>");
builder.AppendLine($"<li></li>");
}
}
string fragmentsHtml = builder.AppendLine("</ul>").ToString();
// The resulting fragmentsHtml:
// ============================
// <ul>
// <li>Doc: employees/2-A</li>
// <li>Fragment: to sales <b style="background:yellow">manager</b> in January</li>
// <li>Doc: employees/5-A</li>
// <li>Fragment: to sales <b style="background:yellow">manager</b> in March</li>
// <li></li>
// </ul>
Highlight results - Map-Reduce index
Configure a Map-Reduce index for highlighting:
To search and get fragments with highlighted terms in a Map-Reduce index:
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The index-field on which you search must be configured with:
FieldStorage.Yes
- store the field in the indexFieldIndexing.Search
- allow Full-Text searchFieldTermVector.WithPositionsAndOffsets
- store the term's position and offsets
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The index-field by which you group-by must configured with:
FieldStorage.Yes
- store the field in the index
// Define a Map-Reduce index:
// ==========================
public class ContactDetailsPerCountry :
AbstractIndexCreationTask<Company, ContactDetailsPerCountry.IndexEntry>
{
// The IndexEntry class defines the index-fields
public class IndexEntry
{
public string Country { get; set; }
public string ContactDetails { get; set; }
}
public ContactDetailsPerCountry()
{
// The 'Map' function defines what will be indexed from each document in the collection
Map = companies => from company in companies
select new IndexEntry
{
Country = company.Address.Country,
ContactDetails = $"{company.Contact.Name} {company.Contact.Title}"
};
// The 'Reduce' function specifies how data is grouped and aggregated
Reduce = results => from result in results
group result by result.Country into g
select new IndexEntry
{
// Set 'Country' as the group-by key
// 'ContactDetails' will be grouped per 'Country'
Country = g.Key,
// Specify the aggregation
// here we use string.Join as the aggregation function
ContactDetails = string.Join(" ", g.Select(x => x.ContactDetails))
};
// Configure index-field 'Country' for Highlighting:
// =================================================
Store(x => x.Country, FieldStorage.Yes);
// Configure index-field 'ContactDetails' for Highlighting:
// ========================================================
Store(x => x.ContactDetails, FieldStorage.Yes);
Index(x => x.ContactDetails, FieldIndexing.Search);
TermVector(x => x.ContactDetails, FieldTermVector.WithPositionsAndOffsets);
}
}
Query the index:
// Define the key by which the resulting fragments are grouped:
// ============================================================
HighlightingOptions options = new HighlightingOptions
{
// Set 'GroupKey' to be the index's group-by key
// The resulting fragments will be grouped per 'Country'
GroupKey = "Country"
};
// Query the map-reduce index:
// ===========================
List<ContactDetailsPerCountry.IndexEntry> detailsPerCountry = session
.Query<ContactDetailsPerCountry.IndexEntry, ContactDetailsPerCountry>()
// Search for results containing the term 'agent'
.Search(x => x.ContactDetails, "agent")
// Request to highlight the searched term by calling 'Highlight'
// Pass the defined 'options'
.Highlight(x => x.ContactDetails, 35, 2, options, out Highlightings agentHighlights)
.ToList();
// Define the key by which the resulting fragments are grouped
// ===========================================================
HighlightingOptions options = new HighlightingOptions
{
// Set 'GroupKey' to be the index's group-by key
// The resulting fragments will be grouped per 'Country'
GroupKey = "Country"
};
// Query the map-reduce index:
// ===========================
List<ContactDetailsPerCountry.IndexEntry> detailsPerCountry = await asyncSession
.Query<ContactDetailsPerCountry.IndexEntry, ContactDetailsPerCountry>()
// Search for results containing the term 'agent'
.Search(x => x.ContactDetails, "agent")
// Request to highlight the searched term by calling 'Highlight'
// Pass the defined 'options'
.Highlight(x => x.ContactDetails, 35, 2, options, out Highlightings agentHighlights)
.ToListAsync();
// Define the key by which the resulting fragments are grouped
// ===========================================================
HighlightingOptions options = new HighlightingOptions
{
// Set 'GroupKey' to be the index's group-by key
// The resulting fragments will be grouped per 'Country'
GroupKey = "Country"
};
// Query the map-reduce index:
// ===========================
List<ContactDetailsPerCountry.IndexEntry> detailsPerCountry = session.Advanced
.DocumentQuery<ContactDetailsPerCountry.IndexEntry, ContactDetailsPerCountry>()
// Search for results containing the term 'agent'
.Search(x => x.ContactDetails, "agent")
// Request to highlight the searched term by calling 'Highlight'
// Pass the defined 'options'
.Highlight(x => x.ContactDetails, 35, 2, options, out Highlightings agentHighlights)
.ToList();
from index "ContactDetailsPerCountry"
where search(ContactDetails, "agent")
include highlight(ContactDetails, 35, 2, $p0)
{"p0":{"GroupKey":"Country"}}
Process results:
// 'detailsPerCountry' contains the contacts details grouped per country.
// 'agentHighlights' contains the text FRAGMENTS that highlight the 'agent' term.
StringBuilder builder = new StringBuilder().AppendLine("<ul>");
foreach (var item in detailsPerCountry)
{
// Call 'GetFragments' to get all fragments for the specified country key
string[] fragments = agentHighlights.GetFragments(item.Country);
foreach (var fragment in fragments)
{
builder.AppendLine($"<li>Country: {item.Country}</li>");
builder.AppendLine($"<li>Fragment: {fragment}</li>");
builder.AppendLine($"<li></li>");
}
}
string fragmentsHtml = builder.AppendLine("</ul>").ToString();
// The resulting fragmentsHtml:
// ============================
// <ul>
// <li>Country: UK</li>
// <li>Fragment: Devon Sales <b style="background:yellow">Agent</b> Helen Bennett</li>
// <li></li>
// <li>Country: France</li>
// <li>Fragment: Sales <b style="background:yellow">Agent</b> Carine Schmit</li>
// <li></li>
// <li>Country: France</li>
// <li>Fragment: Saveley Sales <b style="background:yellow">Agent</b> Paul Henriot</li>
// <li></li>
// <li>Country: Argentina</li>
// <li>Fragment: Simpson Sales <b style="background:yellow">Agent</b> Yvonne Moncad</li>
// <li></li>
// <li>Country: Argentina</li>
// <li>Fragment: Moncada Sales <b style="background:yellow">Agent</b> Sergio</li>
// <li></li>
// <li>Country: Brazil</li>
// <li>Fragment: Sales <b style="background:yellow">Agent</b> Anabela</li>
// <li></li>
// <li>Country: Belgium</li>
// <li>Fragment: Dewey Sales <b style="background:yellow">Agent</b> Pascale</li>
// <li></li>
// </ul>
Customize highlight tags
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Default tags:
- Please refer to Highlight tags to learn about the default html tags used to wrap the highlighted terms.
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Customizing tags:
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The default html tags that wrap the highlighted terms can be customized to any other tags.
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Customizing the wrapping tags when querying an index is done exactly the same as when making
a dynamic query where aHighlightingOptions
object is passed to theHighlight
method. -
Follow the example in Highlight - customize tags.
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