Closes #148 Refactored Where structure to a binary tree for lazy evaluation #149
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| * ``` | ||
| * WHERE (data1 = 'johnson' AND data1 = 'colorado') | ||
| * ``` | ||
| * ### Binary tree structure |
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Oh boy! I happen to have built myself a binary tree 😁 Those interview leet code questions coming in to save the day!!!
| */ | ||
| private fun where(field: Field, operator: String, value: Any?, options: String? = null): String { | ||
| var where = "${field.columnName} $operator ${value.toSqlString()}" | ||
| class Where<out T : Field> private constructor( |
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The primary constructor is private. Two secondary constructors are exposed to uphold the integrity of the binary tree structure.
| options = options | ||
| ) | ||
| } else if (lhs is WhereHolder && rhs is WhereHolder) { | ||
| // Recursive case. Traverse tree. |
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Who knew that recursion would actually come in handy once in a while 🤣
| // If there are mutable property values, then this will be evaluated at the time of invocation | ||
| // and will not mutate along with the mutable property values (e.g. a mutable list). I don't | ||
| // think consumers expect this to mutate anyways if they happen to save a reference to it. | ||
| private val evaluatedWhereString: String by unsafeLazy { |
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Here is where the transformation into a string occurs. Should be self-explanatory 😁
| private val evaluatedWhereString: String by unsafeLazy { | ||
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| var whereString = when (operator) { | ||
| is Operator.Combine -> "($lhs) $operator ($rhs)" |
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With the current structure, the Combine operators (AND, OR) imply that the lhs and rhs are both un-evaluated Where statements. So, this is recursion once again 😁
Most of the details are in #148.
The gist of this change is that the intrinsic value an instance of
Whereis now lazily evaluated. Previously,Whereonly held a reference to the evaluated string. Now, it holds a reference to the left-hand-side, operator, and right-hand-side in a binary tree structure.This will allow us to support things that need
Whereto be mutated, such as #148 and #142.