Refactor Dockerfile to use multi-stage builds (#2004)

docker/Dockerfile

@@ -16,30 +16,41 @@
 # limitations under the License.
 #
 
-FROM postgres:12
+# Build stage: Install necessary development tools for compilation and installation
+FROM postgres:12 AS build
 
 RUN apt-get update \
     && apt-get install -y --no-install-recommends --no-install-suggests \
        bison \
        build-essential \
        flex \
-       postgresql-server-dev-12 \
-       locales
-
-ENV LANG=en_US.UTF-8
-ENV LC_COLLATE=en_US.UTF-8
-ENV LC_CTYPE=en_US.UTF-8
-
-RUN echo "en_US.UTF-8 UTF-8" > /etc/locale.gen \
-    && locale-gen \
-    && update-locale LANG=en_US.UTF-8
+       postgresql-server-dev-12
 
 COPY . /age
 
 WORKDIR /age
 
 RUN make && make install
 
+
+# Final stage: Create a final image by copying the files created in the build stage
+FROM postgres:12
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends --no-install-suggests \
+    locales
+
+RUN echo "en_US.UTF-8 UTF-8" > /etc/locale.gen \
+    && locale-gen \
+    && update-locale LANG=en_US.UTF-8
+
+ENV LANG=en_US.UTF-8
+ENV LC_COLLATE=en_US.UTF-8
+ENV LC_CTYPE=en_US.UTF-8
+
+COPY --from=build /usr/lib/postgresql/12/lib/age.so /usr/lib/postgresql/12/lib/
+COPY --from=build /usr/share/postgresql/12/extension/age--1.5.0.sql /usr/share/postgresql/12/extension/
+COPY --from=build /usr/share/postgresql/12/extension/age.control /usr/share/postgresql/12/extension/
 COPY docker/docker-entrypoint-initdb.d/00-create-extension-age.sql /docker-entrypoint-initdb.d/00-create-extension-age.sql
 
 CMD ["postgres", "-c", "shared_preload_libraries=age"]