Speedup address_to_logs query

CHANGELOG.md

@@ -3,12 +3,11 @@
 ### Features
 
 ### Fixes
+- [#2924](https://github.com/poanetwork/blockscout/pull/2924) - Speedup address to logs query
 - [#2906](https://github.com/poanetwork/blockscout/pull/2906) - fix address sum cache
-
 - [#2902](https://github.com/poanetwork/blockscout/pull/2902) - Offset in blocks retrieval for average block time
 
 ### Chore
-
 - [#2896](https://github.com/poanetwork/blockscout/pull/2896) - Disable Parity websockets tests
 
 

apps/explorer/lib/explorer/chain.ex

@@ -358,22 +358,31 @@ defmodule Explorer.Chain do
     base_query =
       from(log in Log,
         inner_join: transaction in Transaction,
-        on:
-          transaction.block_hash == log.block_hash and transaction.block_number == log.block_number and
-            transaction.hash == log.transaction_hash,
-        order_by: [desc: transaction.block_number, desc: transaction.index],
-        preload: [:transaction, transaction: [to_address: :smart_contract]],
+        on: transaction.hash == log.transaction_hash,
+        order_by: [desc: log.block_number, desc: log.index],
         where: transaction.block_number < ^block_number,
         or_where: transaction.block_number == ^block_number and transaction.index > ^transaction_index,
         or_where:
           transaction.block_number == ^block_number and transaction.index == ^transaction_index and
             log.index > ^log_index,
-        where: log.address_hash == ^address_hash and log.block_hash == transaction.block_hash,
+        where: log.address_hash == ^address_hash,
         limit: ^paging_options.page_size,
         select: log
       )
 
-    base_query
+    wrapped_query =
+      from(
+        log in subquery(base_query),
+        inner_join: transaction in Transaction,
+        preload: [:transaction, transaction: [to_address: :smart_contract]],
+        where:
+          log.block_hash == transaction.block_hash and
+            log.block_number == transaction.block_number and
+            log.transaction_hash == transaction.hash,
+        select: log
+      )
+
+    wrapped_query
     |> filter_topic(options)
     |> Repo.all()
     |> Enum.take(paging_options.page_size)

apps/explorer/priv/repo/migrations/20191218120138_logs_block_number_index_index.exs

@@ -0,0 +1,9 @@
+defmodule Explorer.Repo.Migrations.LogsBlockNumberIndexIndex do
+  use Ecto.Migration
+
+  def change do
+    create_if_not_exists(index(:logs, ["block_number DESC, index DESC"]))
+
+    drop_if_exists(index(:logs, [:block_number], name: "logs_block_number_index"))
+  end
+end