Documentation
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Overview ¶
VM implements the virtual machine runtime evaluator for the SQL, FilterQL, and Expression evalutors.
Index ¶
- Variables
- func Eval(ctx expr.EvalContext, arg expr.Node) (value.Value, bool)
- func EvalFilterSelect(sel *rel.FilterSelect, writeContext expr.ContextWriter, ...) (bool, bool)
- func EvalSql(sel *rel.SqlSelect, writeContext expr.ContextWriter, ...) (bool, error)
- func LikeCompare(a, b string) (value.BoolValue, bool)
- func Matches(cr expr.EvalContext, stmt *rel.FilterStatement) (bool, bool)
- func MatchesExpr(cr expr.EvalContext, node expr.Node) (bool, bool)
- func MatchesInc(inc expr.Includer, cr expr.EvalContext, stmt *rel.FilterStatement) (bool, bool)
- func ResolveIncludes(ctx expr.Includer, arg expr.Node) error
- type DateConverter
- type EvalBaseContext
Constants ¶
This section is empty.
Variables ¶
var ( // MaxDepth acts as a guard against potentially recursive queries MaxDepth = 1000 // ErrMaxDepth If we hit max depth on recursion ErrMaxDepth = fmt.Errorf("Recursive Evaluation Error") // ErrUnknownOp an unrecognized Operator in expression ErrUnknownOp = fmt.Errorf("expr: unknown op type") // ErrUnknownNodeType Unhandled Node type for expression evaluation ErrUnknownNodeType = fmt.Errorf("expr: unknown node type") // ErrExecute could not evaluate an expression ErrExecute = fmt.Errorf("Could not execute") )
Functions ¶
func Eval ¶
Eval - Evaluate the given expression (arg Node) against the given context. @ctx is the evaluation context ie the variables/values which the expression will be evaluated against. It may be a simple reader of message/data or any object whhich implements EvalContext.
func EvalFilterSelect ¶
func EvalFilterSelect(sel *rel.FilterSelect, writeContext expr.ContextWriter, readContext expr.EvalContext) (bool, bool)
EvalFilerSelect evaluates a FilterSelect statement from read, into write context
@writeContext = Write results of projection @readContext = Message input, ie evaluate for Where/Filter clause
func EvalSql ¶
func EvalSql(sel *rel.SqlSelect, writeContext expr.ContextWriter, readContext expr.EvalContext) (bool, error)
EvalSql Is a partial SQL statement evaluator (that doesn't get it all right). See exec package for full sql evaluator. Can be used to evaluate a read context and write results to write context. This does not project columns prior to running WHERE.
@writeContext = Write out results of projection @readContext = Message to evaluate does it match where clause? if so proceed to projection
func LikeCompare ¶
LikeCompare takes two strings and evaluates them for like equality
func Matches ¶
func Matches(cr expr.EvalContext, stmt *rel.FilterStatement) (bool, bool)
Matches executes a FilterQL statement against an evaluation context returning true if the context matches.
func MatchesExpr ¶
MatchesExpr executes a expr.Node expression against an evaluation context returning true if the context matches.
func MatchesInc ¶
func MatchesInc(inc expr.Includer, cr expr.EvalContext, stmt *rel.FilterStatement) (bool, bool)
Matches executes a FilterQL statement against an evaluation context returning true if the context matches.
func ResolveIncludes ¶
ResolveIncludes take an expression and resolve any includes so that it does not have to be resolved at runtime. There is also a InlineIncludes alternative in expr pkg which actually re-writes the expression to remove includes and embed the expressions they refer to as part of this expression.
Types ¶
type DateConverter ¶
type DateConverter struct {
HasDateMath bool // Does this have date math in it all?
Node expr.Node // The expression we are extracting datemath from
TimeStrings []string // List of each extracted timestring
// contains filtered or unexported fields
}
DateConverter can help inspect a boolean expression to determine if there is date-math in it. If there is datemath, can calculate the time boundary where the expression may possibly change from true to false. - Must be boolean expression - Only calculates the first boundary - Only calculates POSSIBLE boundary, given complex logic (ors etc) may NOT change.
func NewDateConverter ¶
func NewDateConverter(ctx expr.EvalIncludeContext, n expr.Node) (*DateConverter, error)
NewDateConverter takes a node expression
func (*DateConverter) Boundary ¶
func (d *DateConverter) Boundary() time.Time
Boundary given all the date-maths in this node find the boundary time where this expression possibly will change boolean value. If no boundaries exist, returns time.Time{} (zero time)
type EvalBaseContext ¶
type EvalBaseContext struct {
expr.EvalContext
}
EvalBaseContext base context for expression evaluation
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