## Issue
Closes#5915
## Change
`AbstractAzureCosmosDBNoSqlEmbeddingStore.search()` appended the
metadata filter with `" AND"` and no `WHERE` keyword.
`AzureCosmosDBNoSqlFilterMapper.map()` returns a predicate without a
leading space, so the query read `... FROM c ANDc.category =
"electronics" ORDER BY ...` and Cosmos DB rejected it. Every filtered
vector search failed; unfiltered search was unaffected.
```java
queryBuilder.append(" WHERE ").append(filterMapper.map(request.filter()));
```
The filter is the only predicate here, so this mirrors
`findRelevantWithFullTextSearch`. The full-text methods use `" WHERE ("`
because another predicate follows theirs; #5486 fixed those two and left
`search()` unchanged.
The new `AzureCosmosDbNoSqlSearchQueryTest` mocks `CosmosAsyncContainer`
and captures the `SqlQuerySpec`, asserting the query text without Azure
credentials. It covers the filtered case (`WHERE` present) and the
unfiltered case (no `WHERE`). Reverting the production change makes the
filtered test fail.
Build notes (JDK 17): `mvn -pl langchain4j-azure-cosmos-nosql clean
test` is green — 33 tests, 0 failures, 6 skipped (pre-existing
`@EnabledIfEnvironmentVariable` tests). Spotless passes. The `*IT`
classes need live Azure Cosmos DB credentials and were not run.
## General checklist
- [X] There are no breaking changes (API, behaviour)
- [X] I have added unit and/or integration tests for my change
- [X] The tests cover both positive and negative cases
- [X] I have manually run all the unit and integration tests in the
module I have added/changed, and they are all green
- [ ] I have manually run all the unit and integration tests in the
[core](https://github.com/langchain4j/langchain4j/tree/main/langchain4j-core)
and
[main](https://github.com/langchain4j/langchain4j/tree/main/langchain4j)
modules, and they are all green
<!-- N/A — change is confined to langchain4j-azure-cosmos-nosql and
touches no core or main module code. -->
- [ ] I have added/updated the
[documentation](https://github.com/langchain4j/langchain4j/tree/main/docs/docs)
<!-- N/A — docs are added after review, per the template note. -->
- [ ] I have added an example in the [examples
repo](https://github.com/langchain4j/langchain4j-examples) (only for
"big" features)
<!-- N/A — bug fix, not a feature. -->
- [ ] I have added/updated [Spring Boot
starter(s)](https://github.com/langchain4j/langchain4j-spring) (if
applicable)
<!-- N/A — no starter covers this store. -->
<!-- "Checklist for adding new maven module" and "Checklist for adding
new embedding store integration" omitted: this PR adds neither. -->
## Checklist for changing existing embedding store integration
- [ ] I have manually verified that the
`{NameOfIntegration}EmbeddingStore` works correctly with the data
persisted using the latest released version of LangChain4j
<!-- Not verified: requires a live Azure Cosmos DB account. The change
only affects query text generation, not the persisted document format.
-->
Eunbin Son
f1d5bccf48