Add a new helper function _CDB_Table_Exists

Makefile

@@ -1,7 +1,7 @@
 # cartodb/Makefile
 
 EXTENSION = cartodb
-EXTVERSION = 0.22.2
+EXTVERSION = 0.22.3
 
 SED = sed
 AWK = awk
@@ -88,6 +88,7 @@ UPGRADABLE = \
   0.22.0 \
   0.22.1 \
   0.22.2 \
+  0.22.3 \
   $(EXTVERSION)dev \
   $(EXTVERSION)next \
   $(END)

scripts-available/CDB_Helper.sql

@@ -158,3 +158,21 @@ BEGIN
   RETURN left(string, (i - 1));
 END;
 $$ LANGUAGE 'plpgsql' IMMUTABLE PARALLEL SAFE;
+
+
+-- Checks if a given text representing a qualified or unqualified table name (relation)
+-- actually exists in the database. It is meant to be used as a guard for other function/queries.
+CREATE FUNCTION cartodb._CDB_Table_Exists(table_name_with_optional_schema TEXT)
+RETURNS bool
+AS $$
+BEGIN
+    IF EXISTS(SELECT * FROM pg_class WHERE table_name_with_optional_schema::regclass::oid = oid AND relkind = 'r') THEN
+       RETURN true;
+    ELSE
+       RETURN false;
+    END IF;
+EXCEPTION
+    WHEN invalid_schema_name OR undefined_table THEN
+        RETURN false;
+END;
+$$ LANGUAGE PLPGSQL VOLATILE PARALLEL SAFE;

test/CDB_HelperTest.sql

@@ -126,3 +126,13 @@ SELECT * FROM cartodb._CDB_Octet_Truncate('piraña', 6);
 
 -- Test _CDB_Octet_Truncate UTF8 case
 SELECT * FROM cartodb._CDB_Octet_Truncate('piraña', 7);
+
+-- Test _CDB_Table_Exists
+CREATE TABLE public.this_table_exists();
+SELECT cartodb._CDB_Table_Exists('this_table_does_not_exist');
+SELECT cartodb._CDB_Table_Exists('this_schema_does_not_exist.this_table_does_not_exist');
+SELECT cartodb._CDB_Table_Exists('this_table_exists');
+SELECT cartodb._CDB_Table_Exists('public.this_table_exists');
+SELECT cartodb._CDB_Table_Exists('raster_overviews'); -- view created by postgis
+SELECT cartodb._CDB_Table_Exists('public.raster_overviews');
+DROP TABLE public.this_table_exists

test/CDB_HelperTest_expect

@@ -57,3 +57,11 @@ DROP TABLE
 pira
 pirañ
 piraña
+CREATE TABLE
+f
+f
+t
+t
+f
+f
+DROP TABLE