The query stack is the ordered list of terms and operators that is generated from the query.
The query stack is printed to the index engine log file up to a maximum of 99 elements.
Example: Query and query stack
For a query:
"global warming" and letter and photo*
you can find the following log file entry:
(Additional line breaks have been inserted for better readability. In the log file viewer, this is shown as one line.)
The query stack items are either terms or operators. Operators are printed in upper case letters and start with OP_. Each operator has the previous expressions as arguments. An expression is either a term or an operator with its arguments.
In the example Query Stack the two arguments to the OR operator on position 9 are:
- the term photosynthesi on position 8
- the expression consisting of the OR operator on position 7 with its two arguments on position 6 and 5
The complete query forms a logical tree, where the nodes are operators and the leaves the words.
Query tree
Note that search mode operators do not show up in the stack. The search mode information is evaluated before the creation of the stack. The mode information is shown as part of the properties of each term in the stack. (In the example shown above, it is exact match for all terms.)