updated canonical header finder functions

2020-11-09 10:29:04 -06:00
parent ca07107cec
commit c0a91b9d9f
8 changed files with 339 additions and 50 deletions
@@ -0,0 +1,110 @@
+-- +goose Up
+ALTER FUNCTION canonical_header RENAME TO canonical_header_id;
+
+-- +goose StatementBegin
+CREATE TYPE child_result AS (
+  has_child BOOLEAN,
+  children eth.header_cids[]
+);
+
+CREATE OR REPLACE FUNCTION has_child(hash VARCHAR(66)) RETURNS child_result AS
+$BODY$
+DECLARE
+  new_child_result child_result;
+BEGIN
+  -- short circuit if there are no children
+  SELECT exists(SELECT 1
+                FROM eth.header_cids
+                WHERE parent_hash = hash
+                LIMIT 1)
+  INTO new_child_result.has_child;
+  -- collect all the children for this header
+  IF new_child_result.has_child THEN
+    SELECT *
+    INTO new_child_result.children
+    FROM eth.header_cids
+    WHERE parent_hash = hash;
+  ELSE
+  END IF;
+  RETURN new_child_result;
+END
+$BODY$
+LANGUAGE 'plpgsql';
+-- +goose StatementEnd
+
+-- +goose StatementBegin
+CREATE OR REPLACE FUNCTION canonical_header_from_set(headers eth.header_cids[]) RETURNS eth.header_cids AS
+$BODY$
+DECLARE
+  canonical_header eth.header_cids;
+  canonical_child eth.header_cids;
+  header eth.header_cids;
+  current_child_result child_result;
+  child_headers eth.header_cids[];
+  current_header_with_child eth.header_cids;
+  has_children_count INT DEFAULT 0;
+BEGIN
+  -- for each header in the provided set
+  FOR header IN SELECT * FROM headers
+  LOOP
+    -- check if it has any children
+    SELECT * INTO current_child_result FROM has_child(header.block_hash);
+    IF current_child_result.has_child THEN
+      -- if it does, take note
+      has_children_count = has_children_count + 1;
+      current_header_with_child = header;
+      -- and add the children to the growing set of child headers
+      child_headers = array_cat(child_headers, current_child_result.children);
+    END IF;
+  END LOOP;
+  -- if none of the headers had children, none is more canonical than the other
+  IF has_children_count = 0 THEN
+    -- return the first one selected
+    SELECT * INTO canonical_header FROM headers LIMIT 1;
+  -- if only one header had children, it can be considered the heaviest/canonical header of the set
+  ELSIF has_children_count = 1 THEN
+    -- return the only header with a child
+    canonical_header = current_header_with_child;
+  -- if there are multiple headers with children
+  ELSE
+    -- find the canonical the canonical header from the child set
+    canonical_child = canonical_header_from_set(child_headers);
+    -- the header that is parent to this header, is the canonical header at this level
+    SELECT * INTO canonical_header FROM headers
+    WHERE block_hash = canonical_child.parent_hash;
+  END IF;
+  RETURN canonical_header;
+END
+$BODY$
+LANGUAGE 'plpgsql';
+-- +goose StatementEnd
+
+-- +goose StatementBegin
+CREATE OR REPLACE FUNCTION canonical_header(height BIGINT) RETURNS eth.header_cids AS
+$BODY$
+DECLARE
+  header_count INT;
+  headers eth.header_cids[];
+BEGIN
+  -- collect every header at this height, noting how many are collected
+  SELECT *, count(*)
+  INTO headers, header_count
+  FROM eth.header_cids
+  WHERE block_number = height;
+  -- if only one header is present, it can be considered canonical (if no header is present we will throw an error)
+  IF header_count = 1 THEN
+    RETURN headers[0];
+  END IF;
+  -- otherwise, if there are multiple headers at this height, we need to determine which is canonical
+  RETURN canonical_header_from_set(headers);
+END
+$BODY$
+LANGUAGE 'plpgsql';
+-- +goose StatementEnd
+
+-- +goose Down
+DROP FUNCTION canonical_header;
+DROP FUNCTION canonical_header_from_set;
+DROP FUNCTION has_child;
+DROP TYPE child_result;
+ALTER FUNCTION canonical_header_id RENAME TO canonical_header;