Azure AI Search supports geo-spatial queries in OData filter expressions via the geo.distance and geo.intersects functions. The geo.distance function returns the distance in kilometers between two points, one being a field or range variable, and one being a constant passed as part of the filter. The geo.intersects function returns true if a given point is within a given polygon, where the point is a field or range variable and the polygon is specified as a constant passed as part of the filter.
Azure AI Search supports various queries in OData filter expressions. We can create a custom BaseAzureSearchIndexingStrategy and GeoLocationSearchModel to implement geo-spatial queries.
public class GeoLocationSearchModel : BaseAzureSearchModel
{
[SearchableField]
public string Title { get; set; }
[SimpleField(IsSortable = true, IsFilterable = true, IsKey = false)]
public GeoPoint GeoLocation { get; set; }
[SearchableField(IsSortable = true, IsFilterable = true, IsFacetable = true)]
public string Location { get; set; }
}Note that GeoPoint is defined in Azure.Core.GeoJson which is part of Azure.Search.Documents NuGet package
Let's say we specified CafePage in the admin ui.
Now we implement how we want to save CafePage page in our strategy.
public class GeoLocationSearchStrategy : BaseAzureSearchIndexingStrategy<GeoLocationSearchModel>
{
private readonly StrategyHelper strategyHelper;
public GeoLocationSearchStrategy(StrategyHelper strategyHelper) => this.strategyHelper = strategyHelper;
public override async Task<IAzureSearchModel> MapToAzureSearchModelOrNull(IIndexEventItemModel item)
{
var result = new GeoLocationSearchModel();
// IIndexEventItemModel could be a reusable content item or a web page item, so we use
// pattern matching to get access to the web page item specific type and fields
if (item is IndexEventWebPageItemModel indexedPage)
{
if (string.Equals(item.ContentTypeName, CafePage.CONTENT_TYPE_NAME, StringComparison.OrdinalIgnoreCase))
{
// The implementation of GetPage<T>() is below
var page = await strategyHelper.GetPage<CafePage>(
indexedPage.ItemGuid,
indexedPage.WebsiteChannelName,
indexedPage.LanguageName,
CafePage.CONTENT_TYPE_NAME);
if (page is null)
{
return null;
}
result.Title = page?.CafeTitle ?? string.Empty;
result.Location = page?.CafeLocation ?? string.Empty;
//We can use this value later to sort by distance from the user accessing our search page.
//Example for this scenario is shown in DancingGoatSearchService.GeoSearch
result.GeoLocation = new GeoPoint((double)page.CafeLocationLatitude, (double)page.CafeLocationLongitude);
}
else
{
return null;
}
}
else
{
return null;
}
return result;
}
}Add an OrderBy option to SearchOptions
public class GeoSearchService
{
private readonly IAzureSearchQueryClientService searchClientService;
public GeoSearchService(IAzureSearchQueryClientService searchClientService) => this.searchClientService = searchClientService;
public async Task<GeoLocationSearchViewModel> GeoSearch(
string indexName,
string searchText,
double latitude,
double longitude,
bool sortByDistance = true,
int page = 1,
int pageSize = 10
)
{
var index = searchClientService.CreateSearchClientForQueries(indexName);
page = Math.Max(page, 1);
pageSize = Math.Max(1, pageSize);
var options = new SearchOptions
{
IncludeTotalCount = true,
Size = pageSize,
Skip = (page - 1) * pageSize
};
if (sortByDistance)
{
options.OrderBy.Add($"geo.distance({nameof(GeoLocationSearchModel.GeoLocation)}, geography'POINT({longitude} {latitude})') asc");
}
options.Select.Add(nameof(GeoLocationSearchModel.Title));
options.Select.Add(nameof(GeoLocationSearchModel.Url));
options.Select.Add(nameof(GeoLocationSearchModel.Location));
var response = await index.SearchAsync<GeoLocationSearchModel>(searchText, options);
return new GeoLocationSearchViewModel
{
Hits = response.Value.GetResults().Select(x => new GeoLocationSearchResult()
{
Title = x.Document.Title,
Url = x.Document.Url,
Location = x.Document.Location,
}),
TotalHits = (int)response.Value.TotalCount,
Query = searchText,
TotalPages = (int)response.Value.TotalCount <= 0 ? 0 : ((int)response.Value.TotalCount - 1) / pageSize + 1,
PageSize = pageSize,
Page = page
};
}
}Map Retrieved SearchModel data to a more simple GeoLocationSearchResult
public class GeoLocationSearchResult
{
public string Title { get; set; } = string.Empty;
public string Url { get; set; } = string.Empty;
public string Location { get; set; } = string.Empty;
}Create a ViewModel
public class GeoLocationSearchViewModel
{
public int TotalHits { get; set; }
public string Query { get; set; }
public int TotalPages { get; set; }
public int PageSize { get; set; }
public int Page { get; set; }
public double Longitude { get; set; }
public double Latitude { get; set; }
public string IndexName { get; set; }
public bool SortByDistance { get; set; } = true;
public string Endpoint { get; set; }
public IEnumerable<GeoLocationSearchResult> Hits { get; set; }
}Create a Controller which uses GeoSearchService to display view with search bar.
[Route("[controller]")]
[ApiController]
public class SearchController : Controller
{
private readonly GeoSearchService searchService;
public SearchController(GeoSearchService searchService) => this.searchService = searchService;
[HttpGet(nameof(Geo))]
public async Task<IActionResult> Geo(string? query, double? latitude, double? longitude, bool? sortByDistance, int? pageSize, int? page, string? indexName)
{
var results = await searchService.GeoSearch(indexName ?? "geo", query, latitude ?? 0, longitude ?? 0, sortByDistance ?? true, page ?? 1, pageSize ?? 10);
results.Endpoint = nameof(Geo);
return View("~/Views/Search/GeoSearch.cshtml", results);
}
}Return a view.
@model GeoLocationSearchViewModel
@{
Dictionary<string, string> GetRouteData(int page) =>
new Dictionary<string, string>() {
{ "query", Model.Query },
{ "pageSize", Model.PageSize.ToString() },
{ "page", page.ToString() },
{ "latitude", Model.Latitude.ToString() },
{ "longitude", Model.Longitude.ToString() },
{ "sortByDistance", Model.SortByDistance.ToString() },
{ "indexName", Model.IndexName }
};
}
<h1>Search</h1>
<style>
.form-field {
margin-bottom: 0.8rem;
}
</style>
<form asp-action=@Model.Endpoint method="get">
<div class="row">
<div class="col-md-12">
<div class="form-field">
<label class="control-label" asp-for="@Model.Query"></label>
<div class="editing-form-control-nested-control">
<input class="form-control" asp-for="@Model.Query" name="query">
<input type="hidden" asp-for="@Model.PageSize" name="pageSize" />
<input type="hidden" asp-for="@Model.Page" name="page" />
<input type="hidden" id="latitude" asp-for="@Model.Latitude" name="latitude"/>
<input type="hidden" id="longitude" asp-for="@Model.Longitude" name="longitude"/>
<input type="hidden" asp-for="@Model.IndexName" name="indexName" />
</div>
</div>
</div>
</div>
<label for="sortByDistance">Sort By Distance</label>
<input type="checkbox" id="sortByDistance" value="true" asp-for="@Model.SortByDistance" name="sortByDistance">
<input type="submit" value="Submit">
</form>
@if (!Model.Hits.Any())
{
if (!String.IsNullOrWhiteSpace(Model.Query))
{
@HtmlLocalizer["Sorry, no results match {0}", Model.Query]
}
return;
}
@foreach (var item in Model.Hits)
{
<div class="col-sm-12">
<div class="section-text">
<h3 class="h4 search-tile-title">
<a href="@item.Url">@item.Title</a>
</h3>
<div>
@Html.Raw(item.Location)
</div>
</div>
</div>
}
<div class="pagination-container">
<ul class="pagination">
@if (Model.Page > 1)
{
<li class="PagedList-skipToPrevious">
<a asp-controller="Search" asp-all-route-data="GetRouteData(Model.Page - 1)">
@HtmlLocalizer["previous"]
</a>
</li>
}
@for (int pageNumber = 1; pageNumber <= Model.TotalPages; pageNumber++)
{
if (pageNumber == Model.Page)
{
<li class="active">
<span>
@pageNumber
</span>
</li>
}
else
{
<li>
<a asp-controller="Search" asp-all-route-data="GetRouteData(pageNumber)">@pageNumber</a>
</li>
}
}
@if (Model.Page < Model.TotalPages)
{
<li class="PagedList-skipToNext">
<a asp-controller="Search" asp-all-route-data="GetRouteData(Model.Page + 1)">
@HtmlLocalizer["next"]
</a>
</li>
}
</ul>
</div>
<script>
document.addEventListener("DOMContentLoaded", function() {
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(function(position) {
document.getElementById('latitude').value = position.coords.latitude;
document.getElementById('longitude').value = position.coords.longitude;
});
} else {
alert("Geolocation is not supported by this browser.");
}
});
</script>