solr fuzzy search with edit distance above 1 - solr

Question

Enviornment- java version "11.0.12" 2021-07-20 LTS, solr-8.9.0
I have the following field declaration for my Solr index:
<field name="Field1" type="string" multiValued="false" indexed="false" stored="true"/>
<field name="author" type="text_general" multiValued="false" indexed="true" stored="true"/>
<field name="Field2" type="string" multiValued="false" indexed="false" stored="true"/>
Field type:
<fieldType name="text_general" class="solr.TextField" positionIncrementGap="100" multiValued="true">
<analyzer type="index">
<tokenizer class="solr.StandardTokenizerFactory"/>
<filter class="solr.LowerCaseFilterFactory"/>
</analyzer>
<analyzer type="query">
<tokenizer class="solr.StandardTokenizerFactory"/>
<filter class="solr.LowerCaseFilterFactory"/>
</analyzer>
</fieldType>
Solr-core has been created using command : ./solr create -c fuzzyCore
The .csv file used to indexed the data is https://drive.google.com/file/d/1z684x2GKsSQWGAdyi6O4uKit4a96iiuh/view
I understand that "Lucene supports fuzzy searches based on the Levenshtein Distance, or Edit Distance algorithm. To do a fuzzy search the tilde, "~", symbol at the end of a Single word Term is used.
~ operator is used to run fuzzy searches. We need to add ~ operator after every single term and can also specify distance which is optional after that as below."
{FIELD_NAME:TERM_1~{Edit_Distance}
Since 'KeywordTokenizer' keeps the whole input as a single token and I want each word to be searchable, so 'StandardTokenizer' is used.
request looks like as mentioned below :
curl "http://localhost:8983/solr/fuzzyCore/select" --data-urlencode "q=author:beaeb~' AND Field1:(w1 x)" --data-urlencode "rows=20"
{
"responseHeader":{
"status":0,
"QTime":14,
"params":{
"q":"author:beaeb~' AND Field1:(w1 x)",
"rows":"20"}},
"response":{"numFound":12,"start":0,"numFoundExact":true,"docs":[
{
"Field1":"x",
"author":"bbaeb",
"Field2":"o",
"id":"f8fbb58d-9e0d-47b2-aa3c-e3920e25a7d1",
"_version_":1746912583192936455},
{
"Field1":"x",
"author":"beabe",
"Field2":"p",
"id":"7d73e7ba-8455-4eb4-818f-1e19b1d35a22",
"_version_":1746912583244316680},
{
"Field1":"x",
"author":"baeeb",
"Field2":"n",
"id":"b4e86fc3-7ecc-407b-b638-88d167a66934",
"_version_":1746912583292551181},
{
"Field1":"x",
"author":"beaea",
"Field2":"o",
"id":"131ad4de-eaa2-47b8-b58b-e690316eed1c",
"_version_":1746912583314571267},
{
"Field1":"x",
"author":"bbaeb",
"Field2":"q",
"id":"d034e66c-a302-4b24-a186-5a2bafecab40",
"_version_":1746912583392165900},
{
"Field1":"x",
"author":"beacb",
"Field2":"n",
"id":"c0ab3e48-2b2d-438d-8cc2-1acfcf6efde8",
"_version_":1746912583490732036},
{
"Field1":"x",
"author":"aeabe",
"Field2":"m",
"id":"4472ec5d-eace-446f-b1d6-c8911be24368",
"_version_":1746912583266336776},
{
"Field1":"x",
"author":"baeab",
"Field2":"q",
"id":"b4c24da3-9199-4eba-a8a3-e30fc17d9167",
"_version_":1746912583274725377},
{
"Field1":"x",
"author":"aeaea",
"Field2":"n",
"id":"bb17bc26-e392-4fed-ae46-bbdd40af0ac0",
"_version_":1746912583294648329},
{
"Field1":"x",
"author":"aeceb",
"Field2":"p",
"id":"5e5cfe21-ff19-464f-8adf-8b5888c418e4",
"_version_":1746912583296745472},
{
"Field1":"x",
"author":"baeab",
"Field2":"p",
"id":"54a3c8e6-137d-47c3-9192-a5ed1904dc55",
"_version_":1746912583357562889},
{
"Field1":"x",
"author":"aeeeb",
"Field2":"m",
"id":"200694a0-6248-49fd-8182-dac79657e045",
"_version_":1746912583385874444}]
}}
,
The above request is not retrieving output as 'author:bebbeb',although there is author:'bebbeb' is present in data with Field1:w1. This can be
verified with following two commands
curl "http://localhost:8983/solr/fuzzyCore/select" --data-urlencode "q=author:beaeb~' AND Field1:w1"
{
"responseHeader":{
"status":0,
"QTime":4,
"params":{
"q":"author:beaeb~' AND Field1:w1"}},
"response":{"numFound":0,"start":0,"numFoundExact":true,"docs":[]
}}
Although output of following command is
curl "http://localhost:8983/solr/fuzzyCore/select" --data-urlencode "q=Field1:w1"
{
"responseHeader":{
"status":0,
"QTime":1,
"params":{
"q":"Field1:w1"}},
"response":{"numFound":1,"start":0,"numFoundExact":true,"docs":[
{
"Field1":"w1",
"author":"bebbeb",
"Field2":"p",
"id":"4356dff2-ab93-4bab-a4dc-1797db38240c",
"_version_":1746912583504363523}]
}}
so I tried to post everything you need to understand my problem. Any ideas? Why author:'bebbeb' is not resulting as output for input:beaeb~

Answer 1

After debugging Lucene we discovered that there is a parameter called maxExpansions set to 50 by default, which could be extended to 1024.
However, looking at the Solr code, we can see that the FuzzyQuery constructor is only called twice and always uses the default maxExpansions value (for performance reasons); this means fuzzy searches take at most the 50 most similar terms and discard the others. That's why when many documents are indexed and most of the terms are similar (as in your case), some documents may not be returned.
A Solr open-source contribution would be needed to expose this parameter and make the use of this feature more flexible (allowing different values to be set).