store: Add table_stats materialzed view

Signed-off-by: Maksim Dimitrov <dimitrov.maksim@gmail.com>

Author: dimitrovmaksim

store/postgres/migrations/2025-10-30-094807-0000_table_stats_view/down.sql

@@ -0,0 +1 @@
+DROP MATERIALIZED VIEW IF EXISTS info.table_stats;

store/postgres/migrations/2025-10-30-094807-0000_table_stats_view/up.sql

@@ -0,0 +1,35 @@
+CREATE MATERIALIZED VIEW info.table_stats AS
+WITH table_info AS (
+    SELECT
+        s.schemaname AS schema_name,
+        sd.id        AS deployment_id,
+        sd.subgraph  AS subgraph,
+        s.tablename  AS table_name,
+        c.reltuples  AS total_row_count,
+        s.n_distinct AS n_distinct
+    FROM pg_stats s
+    JOIN pg_namespace n ON n.nspname = s.schemaname
+    JOIN pg_class c ON c.relnamespace = n.oid AND c.relname = s.tablename
+    JOIN subgraphs.deployment sd ON sd.id::text = substring(s.schemaname, 4)
+    WHERE
+        s.attname   = 'id'
+        AND s.schemaname LIKE 'sgd%'
+        AND c.relname NOT IN ('poi2$', 'data_sources$')
+)
+SELECT
+    schema_name,
+    deployment_id AS deployment,
+    subgraph,
+    table_name,
+    CASE
+        WHEN n_distinct < 0 THEN (-n_distinct) * total_row_count
+        ELSE n_distinct
+    END::bigint AS entities,
+    total_row_count::bigint AS versions,
+    CASE
+        WHEN total_row_count = 0 THEN 0::float8
+        WHEN n_distinct < 0 THEN (-n_distinct)::float8
+        ELSE n_distinct::numeric / total_row_count::numeric
+    END AS ratio
+FROM table_info
+WITH NO DATA;