>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #3576225. --> Reported by: [nikro](https://www.drupal.org/user/576416) Related to !20 >>> <h3>Problem/Motivation</h3> <p> This module currently creates the collection table, but does not provide a way to choose or manage the pgvector index strategy for the embedding column. </p> <p> This means users cannot configure whether a collection should use <strong>no vector index</strong> (exact search), <strong>HNSW</strong>, or <strong>IVFFlat</strong> when creating a collection. It also means existing collections cannot be updated later to add, remove, or switch the vector index strategy from the UI. </p> <p> For pgvector-backed collections, index strategy is an important performance/configuration choice and should be exposed in the provider configuration flow. </p> <h4>Steps to reproduce</h4> <ol> <li>Configure a Search API index that uses the AI VDB Provider PostgreSQL backend.</li> <li>Create a collection through the current provider (it will auto-create it if it doesn't exist).</li> <li>Observe that the table is created, but there is no option to choose a pgvector index strategy (None / HNSW / IVFFlat).</li> <li>Observe that existing collections also have no UI to change the vector index strategy later.</li> </ol> <h3>Proposed resolution</h3> <p> Add a provider setting for <strong>Vector Index Strategy</strong> with a select element in the Search API/provider configuration UI. </p> <ul> <li><strong>None</strong></li> <li><strong>HNSW</strong></li> <li><strong>IVFFlat</strong></li> </ul> <p> Apply the selected strategy in two places: </p> <ol> <li><strong>Collection creation:</strong> update the client createCollection() flow so it creates the table and, if selected, creates the corresponding pgvector index.</li> <li><strong>Existing collections:</strong> expose the same setting on the edit form and, on save, create/drop/switch the vector index as needed.</li> </ol> <p> The module should support transitions between strategies: </p> <ul> <li>None &rarr; HNSW / IVFFlat</li> <li>HNSW &harr; IVFFlat</li> <li>HNSW / IVFFlat &rarr; None</li> </ul> <p> Show a status message after save indicating whether the index was created/updated/removed successfully, and note that indexing/search availability may take a short time depending on queue/data size. </p> <h3>Drafts -&gt; to actual task status (as of now)</h3> <ol> <li><s>&#9989; Add provider configuration form element (select) for vector index strategy</s> &mdash; <code>buildSettingsForm()</code> override in <code>PostgresProvider</code></li> <li><s>&#9989; Persist the selected strategy in provider/Search API index configuration</s> &mdash; stored in <code>database_settings.vector_index_strategy</code> via Search API server config</li> <li><s>&#9989; Update <code>createCollection()</code> logic to create the selected vector index during collection creation</s> &mdash; handled via <code>ConfigEvents::SAVE</code> subscriber at priority <code>-10</code>, fires after upstream creates the table</li> <li><s>&#9989; Add update logic for existing collections (detect current state, create/drop/switch index on save)</s> &mdash; <code>ensureVectorIndex()</code> compares current strategy+opclass vs desired, drops/recreates only when needed</li> <li><s>&#9989; Add validation/error handling for unsupported or unavailable pgvector index types</s> &mdash; <code>VectorIndexException</code> thrown on failure, caught and logged in subscriber without hard-failing the save</li> <li>&#11036; <strong>Add automated tests</strong> &mdash; no tests exist in this module at all; integration tests require a live pgvector connection which makes them hard to run in CI; unit testing the enum is trivial but low value. Skipping is reasonable, worth noting in the issue.</li> <li>&#11036; <strong>Add/update documentation</strong> &mdash; <code>README.md</code> has a stub <code>## Configuration</code> section with no mention of Search API server setup or index strategies. Could add a short section. Low priority but easy win.</li> </ol>