Test Scenario: I set the "Maximum column length" to 1000, then run a SQL query over a table having a longtext column with a 10M cell content on it. When the results are displayed on the Text tab, the first two rows ( column names header and the "---" separator) are correctly truncated to lhe length 1000 (you can check this by playing with the END key inside the editor of the Text Tab). Then, depending if the longtext column had new lines chars on its content or not, you'll have one or more table content lines on the Text tab output, but the last line of the table content will have a size of 10M chars (verify with the END key), the chars after the 1000th position being just space chars.

I've performed a debug session on ADS to see if this behaviour is a Netbeans editor issue or not, but on the BaseDocument.insertString() method I receive a String parameter whose length is 10M chars. Below is the stacktrace (obtained with ADS v14-dev11) :

org.netbeans.editor.BaseDocument.insertString(BaseDocument.java:742)
\\...\\ .\\हिñçêČάй語简�?한\\.tꄯ∕ꇿꎊ native default.append
\\...\\ .\\हिñçêČάй語简�?한\\.pꈌ⠂⠄ꁙ synchronized.a
\\...\\ .\\हिñçêČάй語简�?한\\.pꈌ⠂⠄ꁙ synchronized.b
com.aquafold.datastudio.queryanalyzer.cꍥ⣿ꏶᝅ.run

Please review the string truncation performed on the caller methods listed on this stack trace. Instead of replacing chars with SPACE chars, the string should be truncated to the desired length.