migrations: create package symbols table and alter symbol_history

For golang/go#37102

Change-Id: Ia09e0cd50b8475b88e74cf99578df1c6e9a9bf5d
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/293951
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

migrations/000068_create_symbols_table.down.sql

@@ -0,0 +1,29 @@
+-- Copyright 2021 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+DROP TABLE symbol_history;
+CREATE TABLE symbol_history (
+    id INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    package_path_id INTEGER NOT NULL,
+    module_path_id INTEGER NOT NULL,
+    symbol_id INTEGER NOT NULL,
+    parent_symbol_id INTEGER NOT NULL,
+    since_version TEXT NOT NULL,
+    section symbol_section NOT NULL,
+    synopsis text NOT NULL,
+    type symbol_type,
+    goos goos NOT NULL,
+    goarch goarch NOT NULL,
+
+    UNIQUE(package_path_id, module_path_id, symbol_id, goos, goarch),
+    FOREIGN KEY (parent_symbol_id) REFERENCES symbol_names(id) ON DELETE CASCADE,
+    FOREIGN KEY (module_path_id) REFERENCES paths(id) ON DELETE CASCADE,
+    FOREIGN KEY (symbol_id) REFERENCES symbol_names(id) ON DELETE CASCADE,
+    FOREIGN KEY (package_path_id) REFERENCES paths(id) ON DELETE CASCADE
+);
+DROP TABLE symbols;
+
+END;

migrations/000068_create_symbols_table.up.sql

@@ -0,0 +1,40 @@
+-- Copyright 2021 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+CREATE TABLE package_symbols (
+    id INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    package_path_id INTEGER NOT NULL,
+    module_path_id INTEGER NOT NULL,
+    symbol_name_id INTEGER NOT NULL,
+    parent_symbol_name_id INTEGER NOT NULL,
+    section symbol_section NOT NULL,
+    type symbol_type NOT NULL,
+    synopsis TEXT NOT NULL,
+
+    FOREIGN KEY (symbol_name_id) REFERENCES symbol_names(id) ON DELETE CASCADE,
+    FOREIGN KEY (parent_symbol_name_id) REFERENCES symbol_names(id) ON DELETE CASCADE
+);
+COMMENT ON TABLE package_symbols IS
+'TABLE package_symbols contains information that fully describes symbols that appear in a given package.';
+
+COMMENT ON COLUMN package_symbols.parent_symbol_name_id IS
+'COLUMN package_symbols.parent_symbol_name_id indicates the parent type for a symbol. If the symbol is the parent type, the parent_symbol_id will be equal to the symbol_id.';
+
+DROP TABLE symbol_history;
+CREATE TABLE symbol_history (
+    id INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    package_symbol_id INTEGER NOT NULL,
+    goos goos NOT NULL CHECK(goos != 'all'),
+    goarch goarch NOT NULL CHECK(goarch != 'all'),
+    since_version TEXT NOT NULL CHECK(since_version != ''),
+
+    UNIQUE(package_symbol_id, goos, goarch),
+    FOREIGN KEY (package_symbol_id) REFERENCES package_symbols(id) ON DELETE CASCADE
+);
+COMMENT ON TABLE symbol_history IS
+'TABLE symbol_history documents the first version when a symbol was introduced in a package.';
+
+END;