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IDProjectCategoryView StatusLast Update
07411Feature requestsSurvey editingpublic2021-11-26 07:39
Reportertringate Assigned To 
Status acknowledgedResolutionopen 
Summary07411: Warn survey authors about survey size
DescriptionAvoid writing a survey that is too large to be activated.
Additional InformationA possible solution: Add warning to List survey display with estimated field size shown
Add a column in the survey list screen to give estimated survey table size.

The database type is known, and the estimated table sizes limits are known. A survey could be scanned and an estimated table size shown and those nearing the limits could be displayed in a different color.

Here is what the manual says about table size and unfortunatly after writting a very long survey and then trying to activate it I discovered I was way over the limit of what my database would accept.

...regarding survey size
Note: 'Survey size' refers to the maximmum number of questions (and answers) in your survey - don't confuse this with the number of replies on your survey (there is no limitation on that). Theoretically there would also be no limit on the maximum number of questions/answers in LimeSurvey. But the database engine you are using has several limits. The most important one is the limit on the number of fields(columns) in the result table.

•MySQL ISAM: The sum of the lengths of the VARCHAR and CHAR columns in a table may be up to 64KB.
•MySQL InnoDB: Maximum number of 1000 columns
•MS SQL Server 2000: Maximum number of 1024 columns
•Postgres: Maximum number of 250-1600 columns depending on column types. The maximum number of columns can be quadrupled by increasing the default block size to 32k. See Installation FAQ and PostgreSQL FAQ.

The mySQL ISAM engine is the most tricky one. As it allows only up to 65,535 bytes per row and utf8 characters can require up to three bytes per character the maximum may be only 21,844 characters (but this depends on your DB encoding).
You can roughly calculate the size of your survey like this:

•Every multiple numerical question: 20 chars for each answer
•Every multiple choice & array question answers: 5 chars for each answer
•Every other question type: 5 chars
•Add 10% for the usual overhead
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Bug heat18


related to 05289 acknowledgedc_schmitz Redesign response storage to support more questions+answers (database columns) in a survey 
has duplicate 11099 closedc_schmitz Count number of database columns while building survey. 

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Issue History

Date Modified Username Field Change
2019-11-01 17:25 c_schmitz Category Survey design => Survey editing
2021-03-07 20:43 c_schmitz Relationship added related to 05289
2021-11-26 07:39 c_schmitz Relationship added has duplicate 11099
2021-11-26 07:39 c_schmitz Bug heat 0 => 12
2021-11-26 09:19 guest Bug heat 12 => 18