feature #198 [Store][PG] Allow to change vector type and index type (lyrixx)

This PR was merged into the main branch.

Discussion
----------

[Store][PG] Allow to change vector type and index type

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| Docs?         | no
| Issues        |
| License       | MIT

Gemini gives me vector of 3072 dimms.
But PG vector can' handle that much dimms. [ref](pgvector/pgvector#461)
So a workarround is to change the vectory type, and so the index.

Example:

```
app=# \d gemini
                   Table "public.gemini"
  Column   |     Type      | Collation | Nullable | Default
-----------+---------------+-----------+----------+---------
 id        | uuid          |           | not null |
 metadata  | jsonb         |           |          |
 embedding | halfvec(3072) |           | not null |
Indexes:
    "gemini_pkey" PRIMARY KEY, btree (id)
    "gemini_embedding_idx" hnsw (embedding halfvec_cosine_ops)

app=# select count(*) from gemini ;
 count
-------
   384
(1 row)

```

Commits
-------

83d27e8 [Store][PG] Allow to change vector type and index type

Author: chr-hertel

src/store/src/Bridge/Postgres/Store.php

@@ -120,6 +120,13 @@ public function query(Vector $vector, array $options = [], ?float $minScore = nu
         return $documents;
     }
 
+    /**
+     * @param array{vector_type?: string, vector_size?: positive-int, index_method?: string, index_opclass?: string} $options
+     *
+     * Good configurations $options are:
+     * - For Mistral: ['vector_size' => 1024]
+     * - For Gemini: ['vector_type' => 'halfvec', 'vector_size' => 3072, 'index_method' => 'hnsw', 'index_opclass' => 'halfvec_cosine_ops']
+     */
     public function initialize(array $options = []): void
     {
         $this->connection->exec('CREATE EXTENSION IF NOT EXISTS vector');
@@ -129,20 +136,23 @@ public function initialize(array $options = []): void
                 'CREATE TABLE IF NOT EXISTS %s (
                     id UUID PRIMARY KEY,
                     metadata JSONB,
-                    %s vector(%d) NOT NULL
+                    %s %s(%d) NOT NULL
                 )',
                 $this->tableName,
                 $this->vectorFieldName,
+                $options['vector_type'] ?? 'vector',
                 $options['vector_size'] ?? 1536,
             ),
         );
         $this->connection->exec(
             \sprintf(
-                'CREATE INDEX IF NOT EXISTS %s_%s_idx ON %s USING ivfflat (%s vector_cosine_ops)',
+                'CREATE INDEX IF NOT EXISTS %s_%s_idx ON %s USING %s (%s %s)',
                 $this->tableName,
                 $this->vectorFieldName,
                 $this->tableName,
+                $options['index_method'] ?? 'ivfflat',
                 $this->vectorFieldName,
+                $options['index_opclass'] ?? 'vector_cosine_ops',
             ),
         );
     }