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QLSpec: Add documentation for expression pragmas

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alexet
2022-02-21 18:55:56 +00:00
parent e2bc03c147
commit 5473162f23
1 changed files with 26 additions and 0 deletions
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docs/codeql/ql-language-reference/ql-language-specification.rst
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@@ -1001,6 +1001,7 @@ There are several kinds of expressions:
| postfix_cast
| callwithresults
| aggregation
| expression_pragma
| any
| range
| setliteral
@@ -1306,6 +1307,26 @@ The values of an ``any`` expression are those values of the expression for which
The abbreviated cases for an ``any`` expression are interpreted in the same way as for an aggregation.
Expression Pragma
~~~~~~~~~~~~~~~~
Expression pragmas can be used to guide optimisation.
::
expression_pragma ::= "pragma" "[" expression_pragma_type "]" "(" expr ")"
expression_pragma_type ::= "only_bind_out" | "only_bind_into"
The values of an expression pragma are the values of the expression.
The type `only_bind_out` hints that uses the result of the expression pragma should not be used to guide the evaluation of the result of the contained expression.
When checking to see that all values are bound the compiler does not assume that if the result of the expression pragma is bound then the result of the contained
expression is bound.
The type `only_bind_into` hints that uses the result of expression pragma should not be used to guide the evaluation of the result of the expression pragma.
When checking to see that all values are bound the compiler does not assume that if the result of the contained expression is bound then the result of the
expression pragma is bound.
Ranges
~~~~~~
@@ -2131,6 +2152,7 @@ The complete grammar for QL is as follows:
| postfix_cast
| callwithresults
| aggregation
| expression_pragma
| any
| range
| setliteral
@@ -2162,6 +2184,10 @@ The complete grammar for QL is as follows:
| aggid ("[" expr "]")? "(" as_exprs ("order" "by" aggorderbys)? ")"
| "unique" "(" var_decls "|" (formula)? ("|" as_exprs)? ")"
expression_pragma ::= "pragma" "[" expression_pragma_type "]" "(" expr ")"
expression_pragma_type ::= "only_bind_out" | "only_bind_into"
aggid ::= "avg" | "concat" | "count" | "max" | "min" | "rank" | "strictconcat" | "strictcount" | "strictsum" | "sum"
aggorderbys ::= aggorderby ("," aggorderby)*