Implement CDB_CheckAnalysisQuota

see #279

scripts-available/CDB_AnalysisCheck.sql

@@ -0,0 +1,50 @@
+-- Get the factor (fraction of the quota) for Camshaft cached analysis tables
+CREATE OR REPLACE FUNCTION _CDB_AnalysisQuotaFactor()
+RETURNS float8 AS
+$$
+DECLARE
+  factor float8;
+BEGIN
+  -- We use a floating point cdb_conf parameter
+  SELECT cdb_conf_getconf::text::float8 INTO factor FROM CDB_Conf_GetConf('analysis_cache_factor');
+  -- With a default value
+  IF factor IS NULL THEN
+    factor := 0.2;
+  END IF;
+  RETURN factor;
+END;
+$$
+LANGUAGE 'plpgsql' STABLE;
+
+-- This checks the space used up by Camshaft cached analysis tables.
+-- An exception will be raised if the limits are exceeded.
+-- The name of an analysis table is passed; this, in addition to the
+-- db role that executes this function is used to determined which
+-- analysis tables will be considered.
+CREATE OR REPLACE FUNCTION CDB_CheckAnalysisQuota(table_name TEXT)
+RETURNS void AS
+$$
+DECLARE
+  schema_name TEXT;
+  user_name TEXT;
+  qmax int8;
+  cache_size float8;
+BEGIN
+  -- We rely on the search_path to determine the user's schema and
+  -- check for all analysis tables in that schema.
+  -- An alternative would be to use cdb_analysis_catalog to
+  -- select analysis tables (cache_tables) from the same user, analysis or node.
+  -- For example:
+  --   SELECT unnest(cache_tables) FROM cdb_analysis_catalog
+  --     WHERE username IN (SELECT username FROM cdb_analysis_catalog
+  --       WHERE table_name::regclass = ANY (cache_tables));
+  -- At the moment we're not using the provided table_name.
+
+  SELECT current_schema() INTO schema_name;
+  EXECUTE FORMAT('SELECT %I._CDB_UserQuotaInBytes();', schema_name) INTO qmax;
+  IF qmax*_CDB_AnalysisQuotaFactor() < _CDB_AnalysisDataSize(schema_name) THEN
+    -- The limit is defined by a factor applied to the total space quota for the user
+    RAISE EXCEPTION 'Analysis cache space limits exceeded';
+  END IF;
+END;
+$$ LANGUAGE PLPGSQL;