chore(grouping): migration for hnsw index (#870)

based on analysis
[here](https://github.com/getsentry/data-analysis/blob/main/grouping/hnsw_analysis.ipynb)

---------

Co-authored-by: Matt Duncan <14761+mrduncan@users.noreply.github.com>

src/migrations/versions/d87a6410efe4_migration.py

@@ -0,0 +1,68 @@
+"""Update HNSW parameters for grouping_records
+
+Revision ID: d87a6410efe4
+Revises: a0d00121d118
+Create Date: 2024-07-09 22:28:26.035785
+
+"""
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = "d87a6410efe4"
+down_revision = "a0d00121d118"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.execute("DROP TABLE IF EXISTS grouping_records_new CASCADE;")
+
+    op.execute(
+        """
+        CREATE TABLE grouping_records_new (
+            id BIGINT NOT NULL,
+            project_id BIGINT NOT NULL,
+            hash VARCHAR(32) NOT NULL,
+            message VARCHAR NOT NULL,
+            error_type VARCHAR,
+            stacktrace_embedding VECTOR(768) NOT NULL,
+            PRIMARY KEY (id, project_id)
+        ) PARTITION BY HASH (project_id);
+        """
+    )
+
+    for i in range(100):
+        op.execute(
+            f"""
+            CREATE TABLE grouping_records_new_p{i} PARTITION OF grouping_records_new
+            FOR VALUES WITH (MODULUS 100, REMAINDER {i});
+            """
+        )
+
+    op.execute(
+        """
+        INSERT INTO grouping_records_new (id, project_id, message, error_type, stacktrace_embedding, hash)
+        SELECT id, project_id, message, error_type, stacktrace_embedding, hash
+        FROM grouping_records;
+        """
+    )
+
+    op.execute(
+        """
+        CREATE INDEX ix_grouping_records_new_stacktrace_embedding_hnsw
+        ON grouping_records_new USING hnsw (stacktrace_embedding vector_cosine_ops)
+        WITH (m = 16, ef_construction = 200);
+        """
+    )
+
+    op.execute(
+        "CREATE INDEX ix_grouping_records_new_project_id ON grouping_records_new (project_id);"
+    )
+
+    with op.batch_alter_table("grouping_records_new", schema=None) as batch_op:
+        batch_op.create_unique_constraint("u_project_id_hash_composite", ["project_id", "hash"])
+
+
+def downgrade():
+    op.execute("DROP TABLE IF EXISTS grouping_records_new CASCADE;")

src/seer/db.py

@@ -247,7 +247,7 @@ class DbGroupingRecord(Base):
             "ix_grouping_records_stacktrace_embedding_hnsw",
             "stacktrace_embedding",
             postgresql_using="hnsw",
-            postgresql_with={"m": 16, "ef_construction": 64},
+            postgresql_with={"m": 16, "ef_construction": 200},
             postgresql_ops={"stacktrace_embedding": "vector_cosine_ops"},
         ),
         Index(