Merge pull request #298 from CartoDB/295-estimate-row-count

Add CDB_EstimateRowCount function

.travis.yml

@@ -1,14 +1,41 @@
 language: c
 
 addons:
-  postgresql: 9.3
+  postgresql: 9.5
 
 before_install:
+  # Add custom PPAs from cartodb
+  - sudo add-apt-repository -y ppa:cartodb/postgresql-9.5
+  - sudo add-apt-repository -y ppa:cartodb/gis
+  - sudo add-apt-repository -y ppa:cartodb/gis-testing
   - sudo apt-get update
-  #- sudo apt-get install -q postgresql-9.3-postgis-2.1
-  - sudo apt-get update
-  - sudo apt-get install -q postgresql-server-dev-9.3
-  - sudo apt-get install -q postgresql-plpython-9.3
+
+  # Force instalation of libgeos-3.5.0 (presumably needed because of existing version of postgis)
+  - sudo apt-get -y install libgeos-3.5.0=3.5.0-1cdb2
+
+  # Install postgres db and build deps
+  - sudo /etc/init.d/postgresql stop # stop travis default instance
+  - sudo apt-get -y remove --purge postgresql-9.1
+  - sudo apt-get -y remove --purge postgresql-9.2
+  - sudo apt-get -y remove --purge postgresql-9.3
+  - sudo apt-get -y remove --purge postgresql-9.4
+  - sudo apt-get -y remove --purge postgresql-9.5
+  - sudo rm -rf /var/lib/postgresql/
+  - sudo rm -rf /var/log/postgresql/
+  - sudo rm -rf /etc/postgresql/
+  - sudo apt-get -y remove --purge postgis-2.2
+  - sudo apt-get -y autoremove
+
+  - sudo apt-get -y install postgresql-9.5=9.5.2-3cdb2
+  - sudo apt-get -y install postgresql-server-dev-9.5=9.5.2-3cdb2
+  - sudo apt-get -y install postgresql-plpython-9.5=9.5.2-3cdb2
+  - sudo apt-get -y install postgresql-9.5-postgis-scripts=2.2.2.0-cdb2
+  - sudo apt-get -y install postgresql-9.5-postgis-2.2=2.2.2.0-cdb2
+
+  # configure it to accept local connections from postgres
+  - echo -e "# TYPE  DATABASE        USER            ADDRESS                 METHOD \nlocal   all             postgres                                trust\nlocal   all             all                                     trust\nhost    all             all             127.0.0.1/32            trust" \
+    | sudo tee /etc/postgresql/9.5/main/pg_hba.conf
+  - sudo /etc/init.d/postgresql restart 9.5
 
 script:
   - make

NEWS.md

@@ -1,3 +1,7 @@
+0.19.0 (2017-04-XX)
+
+* Add new function `CDB_EstimateRowCount` #295
+
 0.18.5 (2016-11-30)
 
 * Add to new overview creation strategies #290

doc/CDB_EstimateRowCount.md

@@ -0,0 +1,25 @@
+Estimate the number of rows of a query.
+
+
+#### Using the function
+
+```sql
+SELECT CDB_EstimateRowCount($$
+  UPDATE addresses SET the_geom = cdb_geocode_street_point(addr, city, state, 'US');
+$$) AS row_count;
+```
+
+Result:
+
+```
+ row_count
+-----------
+         5
+(1 row)
+```
+
+#### Arguments
+
+CDB_EstimateRowCount(query)
+
+* **query** text: the SQL query to estimate the row count for.

scripts-available/CDB_EstimateRowCount.sql

@@ -0,0 +1,31 @@
+-- Internal function to generate stats for a table if they don't exist
+CREATE OR REPLACE FUNCTION _CDB_GenerateStats(reloid REGCLASS)
+RETURNS VOID
+AS $$
+DECLARE
+  has_stats BOOLEAN;
+BEGIN
+  SELECT EXISTS (
+    SELECT * FROM pg_catalog.pg_statistic WHERE starelid = reloid
+  ) INTO has_stats;
+  IF NOT has_stats THEN
+    EXECUTE Format('ANALYZE %s;', reloid);
+  END IF;
+END
+$$ LANGUAGE 'plpgsql' VOLATILE STRICT SECURITY DEFINER;
+
+-- Return a row count estimate of the result of a query using statistics
+CREATE OR REPLACE FUNCTION CDB_EstimateRowCount(query text)
+RETURNS Numeric
+AS $$
+DECLARE
+  plan JSON;
+BEGIN
+  -- Make sure statistics exist for all the tables of the query
+  PERFORM _CDB_GenerateStats(tabname) FROM  unnest(CDB_QueryTablesText(query)) AS tabname;
+
+  -- Use the query planner to obtain an estimate of the number of result rows
+  EXECUTE 'EXPLAIN (FORMAT JSON) ' || query INTO STRICT plan;
+  RETURN plan->0->'Plan'->'Plan Rows';
+END
+$$ LANGUAGE 'plpgsql' VOLATILE STRICT;

scripts-enabled/280-CDB_EstimateRowCount.sql

@@ -0,0 +1 @@
+../scripts-available/CDB_EstimateRowCount.sql

test/CDB_DigitSeparatorTest_expect

@@ -1,5 +1,6 @@
 BEGIN
 CREATE TABLE
+COPY 3
 none||
 only_com_dec|.|,
 only_dot_dec|,|.

test/CDB_EstimateRowCountTest.sql

@@ -0,0 +1,10 @@
+SET client_min_messages TO error;
+\set VERBOSITY terse
+CREATE TABLE tmptab1(id INT);
+INSERT INTO tmptab1(id) VALUES (1), (2), (3);
+CREATE TABLE tmptab2(id INT, value NUMERIC);
+INSERT INTO tmptab2(id, value) VALUES (1, 10.0), (2, 20.0);
+SELECT CDB_EstimateRowCount('SELECT SUM(value) FROM tmptab1 INNER JOIN tmptab2 ON (tmptab1.id = tmptab2.id);') AS row_count;
+SELECT CDB_EstimateRowCount('UPDATE tmptab2 SET value = 30 WHERE id=2;') AS row_count;
+DROP TABLE tmptab2;
+DROP TABLE tmptab1;

test/CDB_EstimateRowCountTest_expect

@@ -0,0 +1,9 @@
+SET
+CREATE TABLE
+INSERT 0 3
+CREATE TABLE
+INSERT 0 2
+1
+1
+DROP TABLE
+DROP TABLE

test/CDB_QueryStatementsTest.sql

@@ -1,3 +1,6 @@
+SET client_min_messages TO error;
+\set VERBOSITY terse
+
 WITH q AS ( SELECT CDB_QueryStatements('
 SELECT * FROM geometry_columns;
 ') as statement )

test/CDB_QueryStatementsTest_expect

@@ -1,3 +1,4 @@
+SET
 1|1|SELECT * FROM geometry_columns
 2|1|SELECT * FROM geometry_columns
 3|1|SELECT * FROM geometry_columns

test/CDB_QueryTablesTest.sql

@@ -1,3 +1,5 @@
+SET client_min_messages TO warning;
+\set VERBOSITY terse
 
 WITH inp AS ( select 'SELECT * FROM geometry_columns'::text as q )
  SELECT q, CDB_QueryTables(q) from inp;

test/CDB_QueryTablesTest_expect

@@ -1,17 +1,14 @@
+SET
 SELECT * FROM geometry_columns|{pg_catalog.pg_attribute,pg_catalog.pg_class,pg_catalog.pg_constraint,pg_catalog.pg_namespace,pg_catalog.pg_type}
 SELECT a.attname FROM pg_class c JOIN pg_attribute a on (a.attrelid = c.oid)|{pg_catalog.pg_attribute,pg_catalog.pg_class}
 CREATE table "my'tab;le" as select 1|{}
 SELECT a.oid, b.oid FROM pg_class a, pg_class b|{pg_catalog.pg_class}
 SELECT 1 as col1; select 2 as col2|{}
 WARNING:  CDB_QueryTables cannot explain query: select 1 from nonexistant (42P01: relation "nonexistant" does not exist)
-CONTEXT:  PL/pgSQL function cdb_querytables(text) line 3 at RETURN
 ERROR:  relation "nonexistant" does not exist
-CONTEXT:  PL/pgSQL function cdb_querytables(text) line 3 at RETURN
 begin; select * from pg_class; commit;|{pg_catalog.pg_class}
 WARNING:  CDB_QueryTables cannot explain query: select * from test (42P01: relation "test" does not exist)
-CONTEXT:  PL/pgSQL function cdb_querytables(text) line 3 at RETURN
 ERROR:  relation "test" does not exist
-CONTEXT:  PL/pgSQL function cdb_querytables(text) line 3 at RETURN
 WITH a AS (select * from pg_class) select * from a|{pg_catalog.pg_class}
 CREATE SCHEMA
 CREATE TABLE