Overview

When building the in memory model of the current database state used to evaluate and simulate pending changes, Datical collects row counts from each table. In environments with many tables or with tables that have many rows this operation can become time consuming. As of release 5.7, the collection of row counts changed from a boolean (true | false) to multiple values (exact, approximate, disabled). In older projects, true is mapped to exact and false is mapped to disabled. Using approximate is typically faster than using exact (true).

Note

The default setting starting in v5.7 has changed to disabled (false).

Managing the Project Setting for Row Count Collection

The project setting can be managed in any of the following ways:

GUI: In the project, click the Settings tab. The option is in the Deployment Settings section under Forecast/Deploy: Collect row counts for all tables during Forecast (if needed for rules).
CLI: you can set and show the enableRowCount setting
Datical Service: the setting is in the Project Settings in the Deployment tab.

The setting is one of the following values. It is disabled by default.

exact - Use a table scan to count the rows (uses the most time)
approximate - Use statistics to provide an approximate value (uses less time)
disabled - Do not collect row counts

Database Statistics Used for Approximating Row Counts

The availability and accuracy of table statistics depends on how often you collect and store the statistics on the database server. These details are only for when you set enableRowCount="approximate":

Database	Prerequisite	How Value is Obtained	See Also
Oracle	Run `DBMS_STATS.GATHER_TABLE_STATS` to collect or update the statistics.	Permissions Requires DBA privilege. Source Value in `dba_tables.num_rows` for each table. Sample Query SELECT CONCAT(OWNER,CONCAT('.', TABLE_NAME)) as TABLE_NAME, NUM_ROWS FROM DBA_TABLES WHERE OWNER IN ('&USER_NAME');	Oracle Database Tips
SQL Server	None. Statistics are kept automatically.	Permissions VIEW DATABASE STATE or VIEW SERVER STATE permission SELECT permission on the table object See System Dynamic Management Views Source Uses a `sum` of `row_counts` from `sys.dm_db_partition_stats` to get the total number of rows in the heap or clustered index on the table. Sample Query SELECT (OBJECT_SCHEMA_NAME(object_id)+ '.' + OBJECT_NAME(object_id)) as TABLE_NAME, CAST(row_count AS float) as NUM_ROWS FROM sys.dm_db_partition_stats where OBJECT_SCHEMA_NAME(object_id) IN ('DAT28');	MSDN Blog
DB2	Run `RUNSTATS` to collect or update the statistics.	Permissions The following roles have the necessary permission: ACCESSCTRL DATAACCESS DBADM SECADM SQLADM SYSADM SYSCTRL SYSMAINT SYSMON Source Uses `syscat.tables` view. Sample Query SELECT CONCAT(TRIM(TABSCHEMA), CONCAT('.', TABNAME)) as TABLE_NAME, SUM(CARD) AS NUM_ROWS FROM syscat.tables WHERE TABSCHEMA not in ('SYSIBM', 'SYSPUBLIC', 'SYSCAT', 'SYSSTAT', 'SYSIBMADM', 'SYSTOOLS') and TABSCHEMA in ('db2intuser') GROUP BY TABSCHEMA, TABNAME;	TOOLBOX
EDB Postgres	Perform an ANALYZE before forecast or deploy to get the most accurate values.	Permissions No special permissions required. Source Uses statistics from the catalog table `pg_class`. Sample Query SELECT concat(relnamespace::regnamespace::text,'.',pgc.relname) as TABLE_NAME, pgc.reltuples::BIGINT AS NUM_ROWS FROM pg_class pgc WHERE pgc.relkind='r' and relnamespace::regnamespace::text not in ('pg_catalog', 'information_schema', 'sys', 'public', 'pgagent') and relnamespace::regnamespace::text IN ('SchemaNameHere');	PostgreSQL wiki

Overriding the Row Count Setting in Forecast and Deploy Operations

You can override the project settings when you perform a forecast or deploy operation.

GUI - Set a different value for the option in the Forecast and Deploy wizards.
CLI - Provide a different value in the enableRowCount option for the forecast and deploy commands.

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