sqlite: Functions thats returns the values resulting from a 'SELECT' query and name of column - Feature ISSUE #20565 #20650
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| mut select_header := regex_opt(r'select((\s)+(all)|(distinct)(\s)+)|(\s)+')! | ||
| mut from := regex_opt(r'(\s)+from(\s)+')! |
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hm, why is regex matching needed at all?
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I use the string query itself to obtain the names of the columns if they have been specified, as well as the name of the table! Since there are several ways to initiate the 'SELECT' command doc, I constructed a regex based on the syntax to facilitate obtaining the column names and the table name!
vlib/db/sqlite/sqlite.c.v
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| if select_header.matches_string(query_lower) && query_lower.contains(r'from') { | ||
| // The execution of this function indicates that the passed | ||
| // query is syntactically correct, which is why no additional verification | ||
| rows := db.exec(query)! |
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rows := db.exec(query)! will return an error itself, if the query has invalid syntax.
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Correct, that's why I don't perform any verification other than simply checking if the query is a "select" statement beforehand. If the query isn't a select statement, I don't execute it at all!
That way, I save execution time for a query that isn't even a 'select'.
| if rows.len == 0 { | ||
| return []QuerySet{} | ||
| } else { | ||
| // Finding final index of select((\s)+(all)|(distinct)(\s)+)|(\s)+ inside query_lower string | ||
| _, end_select := select_header.match_string(query_lower) |
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As an aspect of readability, I would mention avoiding unnecessary nested code, with a reference to the book 100 Go Mistakes and How to Avoid Them.
When an if block returns, we should omit the else block [...]
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That should be common sense for any language.
This pull request addresses the feature mentioned in issue #20565 and implements a function that returns the values resulting from a 'SELECT' query and the name of each column. If an alias is provided either through the 'as' command or not, the returned value becomes the alias.
'SELECT SYNTAX' - Documentation
'JOIN SYNTAX' - Documentation
Source code
Examples:
All fields
All names with explicit names
All fields with alias
Specific field
Specific field with alias and 'as'
Specific field with alias without 'as'
All tests are in:
vlib/db/sqlite/sqlite_test.vOUTPUT TESTS