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sp_sync_merge_changes.sql
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sp_sync_merge_changes.sql
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/**********************************************************************************************
Purpose: Sync all changed rows from a source table and merge them into a target table
Notes: * Useful for keeping a up-to-date Redshift copy of a remote Federated table
* Changed rows are found by referring to a `last_modified` timestamp column
* Rows in source that do not exist in target are inserted in target
* Rows in source that match a row in target are updated in target
* Be aware that deletions from the source will not sync to target
* Source and target tables must have same table structure (column order and data types)
Parameters:
batch_time : Timestamp for this batch. Used to timestamp the log
source_tbl : Schema qualified name of external source table
target_tbl : Schema qualified name of local target table
last_mod_col: Name of "last modified" column used to find changed rows
log_table : Schema qualified name of table where actions are logged
CREATE TABLE $(log_table) (
batch_time TIMESTAMP
, source_table VARCHAR
, target_table VARCHAR
, sync_column VARCHAR
, sync_status VARCHAR
, sync_queries VARCHAR --Query ID of the INSERT
, row_count INT);
max_rows : Maximum number of rows allowed to sync automatically
History:
2020-04-01 - joeharris76 - Created
**********************************************************************************************/
-- DROP PROCEDURE sp_sync_merge_changes(TIMESTAMP,VARCHAR,VARCHAR,VARCHAR,VARCHAR,BIGINT);
CREATE OR REPLACE PROCEDURE sp_sync_merge_changes (
batch_time IN TIMESTAMP
, source_tbl IN VARCHAR(256) --Schema qualified with external schema
, target_tbl IN VARCHAR(256) --Schema qualified or `public` is assumed
, last_mod_col IN VARCHAR(128)
, log_table IN VARCHAR(256)
, max_rows IN BIGINT)
AS $$
DECLARE
sql VARCHAR(MAX) := '';
rs_tbl VARCHAR := '';
rs_schm VARCHAR := '';
is_timestamp BOOLEAN := FALSE;
max_mod_ts TIMESTAMP := '1970-01-01';
pk_columns VARCHAR(512) := '';
insert_query VARCHAR := '';
delete_query VARCHAR := '';
sync_count INTEGER := 0;
delete_count INTEGER := 0;
insert_count INTEGER := 0;
change_count INTEGER := 0;
BEGIN
-- Check that required parameters are set
IF source_tbl='' OR target_tbl='' OR last_mod_col='' OR log_table='' OR max_rows IS NULL THEN
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''ABORT - Empty parameters'','''||insert_query||''','||sync_count||';';
COMMIT; --Persist the log entry
RAISE EXCEPTION 'Aborted - required parameters are missing.';
END IF;
-- Notify user when max_rows is specified
IF max_rows <> 0 THEN
RAISE INFO 'A maximum of % rows will be inserted.', max_rows;
END IF;
-- Split `target_tbl` into `rs_schm` and `rs_tbl` as needed
IF CHARINDEX('.',target_tbl) > 0 THEN
SELECT INTO rs_schm SPLIT_PART(target_tbl,'.',1);
SELECT INTO rs_tbl SPLIT_PART(target_tbl,'.',2);
ELSE
rs_schm := 'public';
rs_tbl := target_tbl;
END IF;
--Check that `last_mod_col` is a usable Date/Time value
-- Note: types 1083, 1266, and 1186 are unsupported in Redshift
sql := 'SELECT CASE WHEN a.atttypid IN (1114,1184,1082) THEN TRUE ELSE FALSE END '||
' FROM pg_attribute a '||
' JOIN pg_class b ON a.attrelid = b.relfilenode '||
' JOIN pg_namespace c ON b.relnamespace = c.oid '||
' WHERE TRIM(a.attname) = '''||last_mod_col||''''||
' AND TRIM(c.nspname) = '''||rs_schm||''''||
' AND TRIM(b.relname) = '''||rs_tbl||''''||
'LIMIT 1;';
EXECUTE sql INTO is_timestamp;
IF is_timestamp IS FALSE THEN
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''ABORT - `last_mod_col` is not a date/time'','''||insert_query||''','||sync_count||';';
COMMIT; --Persist the log entry
RAISE EXCEPTION 'Aborted - `%` is not a date/time column.', last_mod_col;
END IF;
--Get the max value of `last_mod_col` in `target_tbl`
sql := 'SELECT MAX('||last_mod_col||') FROM '||target_tbl||' ;';
EXECUTE sql INTO max_mod_ts;
IF max_mod_ts = '1970-01-01' OR max_mod_ts IS NULL THEN
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''ABORT - Invalid `max_mod_ts`'','''||insert_query||''','||sync_count||';';
COMMIT; --Persist the log entry
RAISE EXCEPTION 'Aborted - `max_mod_ts` was not retrieved correctly.';
END IF;
--Retrieve the primary key column(s) for the table
sql := 'SELECT REPLACE(REPLACE(pg_get_constraintdef(con.oid),''PRIMARY KEY ('',''''),'')'','''')'||
' FROM pg_constraint AS con '||
' JOIN pg_class AS tbl ON tbl.relnamespace = con.connamespace AND tbl.oid = con.conrelid'||
' JOIN pg_namespace AS sch ON sch.oid =tbl.relnamespace'||
' WHERE tbl.relkind = ''r'' AND con.contype = ''p''';
EXECUTE sql||' ;' INTO pk_columns;
IF pk_columns = '' THEN
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''ABORT - No PRIMARY KEY found'','''||insert_query||''','||sync_count||';';
COMMIT; --Persist the log entry
RAISE EXCEPTION 'Aborted - No PRIMARY KEY found for target.';
END IF;
-- Create a local temp table with the structure of the target table
-- We can check `max_rows` against the temp table row count and roll back if needed
-- This means we SELECT from the source table **just once**.
EXECUTE 'DROP TABLE IF EXISTS tmp_sp_sync_merge;';
EXECUTE 'CREATE TEMPORARY TABLE tmp_sp_sync_merge (LIKE '||target_tbl||' );';
-- Insert all changed data from source into the temp table
EXECUTE 'INSERT INTO tmp_sp_sync_merge SELECT * FROM '||source_tbl||' WHERE '||quote_ident(last_mod_col)||' > '''||max_mod_ts||''';';
SELECT INTO sync_count COUNT(*) FROM tmp_sp_sync_merge;
-- Roll back if `max_rows` is set and temp table row count exceeds it
IF max_rows <> 0 AND sync_count > max_rows THEN
ROLLBACK;
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''ABORT - Sync exceeds `max_rows`'','''||insert_query||''','||sync_count||';';
COMMIT; --Persist the log entry
RAISE EXCEPTION 'Aborted - Sync row count exceeds `max_rows` value.';
END IF;
IF sync_count > 0 THEN
-- MERGE pt1 - DELETE any changed rows from the target table
EXECUTE 'DELETE FROM '||target_tbl||' WHERE '||pk_columns||' IN (SELECT '||pk_columns||' FROM tmp_sp_sync_merge);';
-- Get row count for the DELETE
GET DIAGNOSTICS delete_count := ROW_COUNT;
-- Get query id for the DELETE
SELECT INTO delete_query pg_last_query_id();
-- MERGE pt2 - INSERT all rows (new and changes) from temp into target
EXECUTE 'INSERT INTO '||target_tbl||' SELECT * FROM tmp_sp_sync_merge;';
-- Get row count for the INSERT
GET DIAGNOSTICS insert_count := ROW_COUNT;
-- Get query id for the INSERT
SELECT INTO insert_query pg_last_query_id();
-- Check modified row count in target before commit
EXECUTE 'SELECT COUNT(*) FROM '||target_tbl||' WHERE '||quote_ident(last_mod_col)||' > '''||max_mod_ts||''';' INTO change_count;
IF sync_count = change_count THEN
-- Commit the merge and record success
COMMIT;
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''SUCCESS'','''||delete_query||', '||insert_query||''','||sync_count||';';
RAISE INFO 'SUCCESS - % rows synced.', sync_count;
-- Otherwise roll back changes
ELSE
ROLLBACK;
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''ABORT - Changed row count was not correct~'','''||delete_query||', '||insert_query||''','||sync_count||';';
COMMIT; -- Persist the log entry
RAISE EXCEPTION 'Aborted - Changed row count did not match expected row count.';
END IF;
ELSE
EXECUTE 'INSERT INTO '||log_table||' (batch_time, source_table, target_table, sync_column, sync_status, sync_queries, row_count)'||
' SELECT '''||batch_time||''','''||source_tbl||''','''||target_tbl||''','''||last_mod_col||
''',''SKIPPED'','''||insert_query||''','||sync_count||';';
RAISE INFO 'SKIPPED - No new or changed rows found.';
END IF;
END
$$ LANGUAGE plpgsql;
/* Usage Example:
-- Redshift: create logging table
DROP TABLE IF EXISTS public.sp_logs;
CREATE TABLE public.sp_logs (
batch_time TIMESTAMP
, source_table VARCHAR
, target_table VARCHAR
, sync_column VARCHAR
, sync_status VARCHAR
, sync_queries VARCHAR
, row_count INT);
-- Redshift: create valid target table and partially populate
DROP TABLE IF EXISTS public.rs_tbl;
CREATE TABLE public.rs_tbl (
pk_col INTEGER PRIMARY KEY
, data_col VARCHAR(20)
, last_mod TIMESTAMP);
INSERT INTO public.rs_tbl
VALUES (1,'aardvark', SYSDATE), (2,'aardvarks', SYSDATE);
-- Redshift: create **invalid** target table to test the SP
DROP TABLE IF EXISTS public.rs_invalid;
CREATE TABLE public.rs_invalid (
pk_col VARCHAR(20) PRIMARY KEY
, data_col VARCHAR(20)
, last_mod VARCHAR);
INSERT INTO public.rs_invalid
VALUES (1,'aardvark', SYSDATE), (2,'aardvarks', SYSDATE);
-- Postgres: create source table and populate with data
DROP TABLE IF EXISTS public.pg_tbl;
CREATE TABLE public.pg_tbl (
pk_col INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY
, data_col VARCHAR(20)
, last_mod TIMESTAMP);
INSERT INTO public.pg_tbl (data_col, last_mod)
VALUES ('aardvark', NOW()),('aardvarks', NOW()),('aardwolf', NOW()),('aardwolves', NOW());
-- Redshift: create external schema for federated database
-- CREATE EXTERNAL SCHEMA IF NOT EXISTS pg_fed
-- FROM POSTGRES DATABASE 'dev' SCHEMA 'public'
-- URI 'aurora-postgres-ro.ch1pch0psh0p.us-west-2.rds.amazonaws.com' PORT 8192
-- IAM_ROLE 'arn:aws:iam::123456789012:role/apg-federation-role'
-- SECRET_ARN 'arn:aws:secretsmanager:us-west-2:123456789012:secret:apg-federation-secret-187Asd';
CREATE EXTERNAL SCHEMA IF NOT EXISTS apg_100g
FROM POSTGRES DATABASE 'tpch_100g' SCHEMA 'public'
URI 'apgf-instance-1.cr7d8lhiupkf.us-west-2.rds.amazonaws.com' PORT 8192
IAM_ROLE 'arn:aws:iam::953075369322:role/apg-fed-test'
SECRET_ARN 'arn:aws:secretsmanager:us-west-2:953075369322:secret:apgf-secret-187Asd'
;
-- Redshift: call the stored procedure using the invalid table
-- CALL sp_sync_merge_changes(SYSDATE,'pg_fed.pg_tbl','public.rs_invalid','last_mod','public.sp_logs',0);
CALL sp_sync_merge_changes(SYSDATE,'apg_100g.pg_tbl','public.rs_invalid','last_mod','public.sp_logs',0);
-- ERROR: Aborted - `pk_col` is not a date/time column.
SELECT * FROM sp_logs ORDER BY batch_time DESC LIMIT 1;
-- -[ RECORD 1 ]+------------------------------------------
-- batch_time | 2020-04-01 17:49:53.413601
-- source_table | apg_100g.pg_tbl
-- target_table | public.rs_invalid
-- sync_column | pk_col
-- sync_status | ABORT - `last_mod_col` is not a date/time
-- sync_queries |
-- row_count | 0
-- Redshift: call the stored procedure using NULL for `max_rows`
-- CALL sp_sync_merge_changes(SYSDATE,'pg_fed.pg_tbl','public.rs_invalid','last_mod','public.sp_logs',NULL);
CALL sp_sync_merge_changes(SYSDATE,'apg_100g.pg_tbl','public.rs_invalid','last_mod','public.sp_logs',NULL);
-- ERROR: Aborted - required parameters are missing.
SELECT * FROM sp_logs ORDER BY batch_time DESC LIMIT 1;
-- -[ RECORD 1 ]+---------------------------
-- batch_time | 2020-04-01 17:47:22.406301
-- source_table | apg_100g.pg_tbl
-- target_table | public.rs_invalid
-- sync_column | pk_col
-- sync_status | ABORT - Empty parameters
-- sync_queries |
-- row_count | 0
-- Redshift: call the stored procedure with empty `last_mod_col`
-- CALL sp_sync_merge_changes(SYSDATE,'pg_fed.pg_tbl','public.rs_tbl','','public.sp_logs',0);
CALL sp_sync_merge_changes(SYSDATE,'apg_100g.pg_tbl','public.rs_tbl','','public.sp_logs',0);
-- ERROR: Aborted - required parameters are missing.
SELECT * FROM sp_logs ORDER BY batch_time DESC LIMIT 1;
-- -[ RECORD 1 ]+---------------------------
-- batch_time | 2020-04-01 17:53:55.863634
-- source_table | apg_100g.pg_tbl
-- target_table | public.rs_tbl
-- sync_column |
-- sync_status | ABORT - Empty parameters
-- sync_queries |
-- row_count | 0
-- Redshift: call the stored procedure with max_rows = 1
-- CALL sp_sync_merge_changes(SYSDATE,'pg_fed.pg_tbl','public.rs_tbl','last_mod','public.sp_logs',1);
CALL sp_sync_merge_changes(SYSDATE,'apg_100g.pg_tbl','public.rs_tbl','last_mod','public.sp_logs',1);
-- INFO: A maximum of 1 rows will be inserted.
-- ERROR: Aborted - Sync row count exceeds `max_rows` value.
SELECT * FROM sp_logs ORDER BY batch_time DESC LIMIT 1;
-- -[ RECORD 1 ]+--------------------------------
-- batch_time | 2020-04-01 18:00:15.649098
-- source_table | apg_100g.pg_tbl
-- target_table | public.rs_tbl
-- sync_column | last_mod
-- sync_status | ABORT - Sync exceeds `max_rows`
-- sync_queries |
-- row_count | 4
-- Redshift: call the stored procedure with max_rows unlimited
CALL sp_sync_merge_changes(SYSDATE,'pg_fed.pg_tbl','public.rs_tbl','last_mod','public.sp_logs',0);
-- INFO: Max of `last_mod_col` is 2020-04-01 17:36:36.392182 .
-- INFO: SUCCESS - 4 rows synced.
SELECT * FROM sp_logs ORDER BY batch_time DESC LIMIT 1;
-- -[ RECORD 1 ]+---------------------------
-- batch_time | 2020-04-01 18:03:21.640183
-- source_table | apg_100g.pg_tbl
-- target_table | public.rs_tbl
-- sync_column | last_mod
-- sync_status | SUCCESS
-- sync_queries | 1254325
-- row_count | 4
-- Redshift: call the stored procedure again
CALL sp_sync_merge_changes(SYSDATE,'pg_fed.pg_tbl','public.rs_tbl','last_mod','public.sp_logs',0);
-- INFO: SKIPPED - No new or changed rows found.
SELECT * FROM sp_logs ORDER BY batch_time DESC LIMIT 1;
-- -[ RECORD 1 ]+---------------------------
-- batch_time | 2020-04-01 18:04:59.511929
-- source_table | apg_100g.pg_tbl
-- target_table | public.rs_tbl
-- sync_column | last_mod
-- sync_status | SKIPPED
-- sync_queries |
-- row_count | 0
*/