Обсуждение: Help to find-the-maximum-length-of-field-in-a-particular-column-in-allthe tables

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On Thursday, April 2, 2020, postgann2020 s <postgann2020@gmail.com> wrote:

Hi Team,

Good Evening,

We are trying to syncing the table field size with other db tables filed size.

I wouldn’t bother fiddling with arbitrary sizes, just remove,them.

 

We have multiple tables in multiple schemas in DB. we are tyring to findout maximum size of each column in table for all tables and for all schemas in DB. 

You need to decide whether you want to query table data or catalog (schema) data.

 

I have tried below query, but not able to get desired output.

SELECT (select column_name from INFORMATION_SCHEMA.COLUMNS where table_name='building'), select max(length(select column_name from INFORMATION_SCHEMA.COLUMNS where table_name='building')) from from INFORMATION_SCHEMA.COLUMNS where table_name='building'
group by column_name;

 

If you want to dynamically determine tables and columns while still checking the actual table data you will need to create a dynamic sql statement to query the actual table with the content for the dynamic schema parts being populated by a query against information_schema or the catalog.  You’d need you something besdies pure sql (e.g., pl/pgsql) to do this.  You may find it easier to just brute force things.

David J.

On Thu, Apr 2, 2020 at 10:15 PM postgann2020 s <postgann2020@gmail.com> wrote:

We are trying to findout the max size of the data in columns for all tables to resize the width of the assigned columns.

If you forgo brute force you will need to combine catalog access with dynamic SQL.  I'm not offering to work out the specific syntax for you.  If you've no better place to start the pl/pgsql documentation works as a language that provides this capability.  The main problem you are solving is that identifiers (e.b., table and column names) in select queries must be provided in the query text so you need to insert them (ideally using the "format()" function and "%I (eye)" placeholder.

I feel it bears repeating that this exercise seems like a poor one to perform (admittedly with zero actual knowledge as to the underlying situation).  Resizing them to "no size restriction" (i.e., "col_name text") would be my preference.  Higher risk fields might warrant constraints that check content in addition to (or in lieu of) length.  That fact that you are wanting to perform this exercise in the first place would be sufficient evidence that the previous decision to have field length limits was a poor one.  That my 0.02

David J.