// Repeat algorithm
// Firstly, we generate the repeatQueryBlock in order that we can get the initial query
// Secondly, we generate the inputVariableVistorMap via repeatInputVariable.ProjectedProperties,
// untilInputVariable.ProjectedProperties, emitInputVariable.ProjectedProperties and ProjectedProperties.
// Generally, these properties are related to the input every time, but in repeatQueryBlock, these are
// just related to the input of the first time. Therefore, we need to replace these after.
// Thirdly, we need to generate the firstQueryExpr and the selectColumnExpr of repeatQueryBlock. Pay
// attention, we need to repeatQueryBlock again because we need more properties about the output of
// the last step in repeat-step. These properties are populated in the second step.
// Fourthly, we use the inputVariableVistorMap to replace the columns in the repeatQueryBlock. But we
// should not change the columns in path-step. Because if we generate the path in the repeat-step, the
// path consists of
// 1. the previous steps before the repeat-step
// 2. the local path(_path) in the repeat-step
// Keep in mind that the initial _path is null, the _path includes all steps as long as they are in
// the repeat-step except for the first input. And the _path after the first pass includes the last step
// in the repeat-step. So the path must include the two part. That means all columns in path-step should
// not be replaced. Here, we use the ModifyRepeatInputVariablesVisitor to finish this work. If it visits
// WPathTableReference, it does nothing, otherwise, it will replace the columns according to the
// inputVariableVistorMap.
public override WTableReference ToTableReference()
{
//The following two variables are used for manually creating SelectScalarExpression of repeat
List <WSelectScalarExpression> firstSelectList = new List <WSelectScalarExpression>();
List <WSelectScalarExpression> secondSelectList = new List <WSelectScalarExpression>();
WScalarExpression firstSelectColumn, secondSelectColumn, firstExpr, secondExpr;
// The following map is used to replace columns of the first input to columns of the repeat input
// such as N_0.id -> R.key_0
string aliasName;
Tuple <string, string> key, value;
Dictionary <Tuple <string, string>, Tuple <string, string> > inputVariableVistorMap =
new Dictionary <Tuple <string, string>, Tuple <string, string> >();
// We should generate the syntax tree firstly
// Some variables will populate ProjectProperty only when we call the ToTableReference function where they appear.
WRepeatConditionExpression repeatConditionExpr = this.GetRepeatConditionExpression();
WSelectQueryBlock repeatQueryBlock = this.RepeatContext.ToSelectQueryBlock();
GremlinVariable repeatInputVariable = this.RepeatContext.VariableList.First();
GremlinVariable repeatOutputVariable = this.RepeatContext.PivotVariable;
GremlinVariable realInputVariable = this.InputVariable.RealVariable;
GremlinVariable repeatPivotVariable = this.RepeatContext.PivotVariable;
// this.DefaultProperty
key = new Tuple <string, string>(this.GetVariableName(), this.DefaultProperty());
value = key;
inputVariableVistorMap[key] = value;
key = new Tuple <string, string>(realInputVariable.GetVariableName(), realInputVariable.DefaultProperty());
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, this.DefaultProperty());
inputVariableVistorMap[key] = value;
firstExpr = realInputVariable.DefaultProjection().ToScalarExpression();
secondExpr = repeatOutputVariable.DefaultProjection().ToScalarExpression();
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstExpr, this.DefaultProperty()));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondExpr, this.DefaultProperty()));
foreach (string property in this.ProjectedProperties)
{
if (property == GremlinKeyword.Path)
{
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(SqlUtil.GetValueExpr(null), GremlinKeyword.Path));
secondSelectList.Add(
SqlUtil.GetSelectScalarExpr(
this.RepeatContext.ContextLocalPath.DefaultProjection().ToScalarExpression(),
GremlinKeyword.Path));
}
else
{
key = new Tuple <string, string>(this.GetVariableName(), property);
value = key;
inputVariableVistorMap[key] = value;
key = new Tuple <string, string>(realInputVariable.GetVariableName(), property);
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, property);
inputVariableVistorMap[key] = value;
firstExpr = realInputVariable.ProjectedProperties.Contains(property)
? realInputVariable.GetVariableProperty(property).ToScalarExpression()
: SqlUtil.GetValueExpr(null);
secondExpr = repeatOutputVariable.ProjectedProperties.Contains(property)
? this.RepeatContext.PivotVariable.GetVariableProperty(property).ToScalarExpression()
: SqlUtil.GetValueExpr(null);
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstExpr, property));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondExpr, property));
}
}
// repeatInputVariable.DefaultProperty()
key = new Tuple <string, string>(repeatInputVariable.GetVariableName(), repeatInputVariable.DefaultProperty());
if (!inputVariableVistorMap.Keys.Contains(key))
{
aliasName = this.GenerateKey();
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, aliasName);
inputVariableVistorMap[key] = value;
firstSelectColumn = repeatInputVariable.DefaultProjection().ToScalarExpression() as WColumnReferenceExpression;
secondSelectColumn = repeatPivotVariable.DefaultProjection().ToScalarExpression() as WColumnReferenceExpression;
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstSelectColumn, aliasName));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondSelectColumn, aliasName));
}
foreach (string property in repeatInputVariable.ProjectedProperties)
{
key = new Tuple <string, string>(repeatInputVariable.GetVariableName(), property);
if (!inputVariableVistorMap.Keys.Contains(key))
{
aliasName = this.GenerateKey();
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, aliasName);
inputVariableVistorMap[key] = value;
firstSelectColumn = repeatInputVariable.GetVariableProperty(property).ToScalarExpression() as WColumnReferenceExpression;
secondSelectColumn = repeatPivotVariable.GetVariableProperty(property).ToScalarExpression() as WColumnReferenceExpression;
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstSelectColumn, aliasName));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondSelectColumn, aliasName));
}
}
if (this.RepeatCondition.TerminationContext != null && this.RepeatCondition.TerminationContext.VariableList.Count > 0)
{
GremlinVariable untilInputVariable = this.RepeatCondition.TerminationContext.VariableList.First();
// untilInputVariable.DefaultProperty()
key = new Tuple <string, string>(untilInputVariable.GetVariableName(), untilInputVariable.DefaultProperty());
if (!inputVariableVistorMap.Keys.Contains(key))
{
aliasName = this.GenerateKey();
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, aliasName);
inputVariableVistorMap[key] = value;
firstSelectColumn =
untilInputVariable.DefaultProjection().ToScalarExpression() as WColumnReferenceExpression;
secondSelectColumn =
repeatPivotVariable.DefaultProjection().ToScalarExpression() as WColumnReferenceExpression;
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstSelectColumn, aliasName));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondSelectColumn, aliasName));
}
foreach (string property in untilInputVariable.ProjectedProperties)
{
key = new Tuple <string, string>(untilInputVariable.GetVariableName(), property);
if (!inputVariableVistorMap.Keys.Contains(key))
{
aliasName = this.GenerateKey();
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, aliasName);
inputVariableVistorMap[key] = value;
firstSelectColumn = untilInputVariable.GetVariableProperty(property).ToScalarExpression() as WColumnReferenceExpression;
secondSelectColumn = repeatPivotVariable.GetVariableProperty(property).ToScalarExpression() as WColumnReferenceExpression;
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstSelectColumn, aliasName));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondSelectColumn, aliasName));
}
}
}
if (this.RepeatCondition.EmitContext != null && this.RepeatCondition.EmitContext.VariableList.Count > 0)
{
GremlinVariable emitInputVariable = this.RepeatCondition.EmitContext.VariableList.First();
// emitInputVariable.DefaultProperty()
key = new Tuple <string, string>(emitInputVariable.GetVariableName(), emitInputVariable.DefaultProperty());
if (!inputVariableVistorMap.Keys.Contains(key))
{
aliasName = this.GenerateKey();
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, aliasName);
inputVariableVistorMap[key] = value;
firstSelectColumn =
emitInputVariable.DefaultProjection().ToScalarExpression() as WColumnReferenceExpression;
secondSelectColumn =
repeatPivotVariable.DefaultProjection().ToScalarExpression() as WColumnReferenceExpression;
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstSelectColumn, aliasName));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondSelectColumn, aliasName));
}
foreach (string property in emitInputVariable.ProjectedProperties)
{
key = new Tuple <string, string>(emitInputVariable.GetVariableName(), property);
if (!inputVariableVistorMap.Keys.Contains(key))
{
aliasName = this.GenerateKey();
value = new Tuple <string, string>(GremlinKeyword.RepeatInitalTableName, aliasName);
inputVariableVistorMap[key] = value;
firstSelectColumn =
emitInputVariable.GetVariableProperty(property).ToScalarExpression() as WColumnReferenceExpression;
secondSelectColumn =
repeatPivotVariable.GetVariableProperty(property).ToScalarExpression() as WColumnReferenceExpression;
firstSelectList.Add(SqlUtil.GetSelectScalarExpr(firstSelectColumn, aliasName));
secondSelectList.Add(SqlUtil.GetSelectScalarExpr(secondSelectColumn, aliasName));
}
}
}
WSelectQueryBlock firstQueryExpr = new WSelectQueryBlock();
foreach (WSelectScalarExpression selectColumnExpr in firstSelectList)
{
firstQueryExpr.SelectElements.Add(selectColumnExpr);
}
repeatQueryBlock = this.RepeatContext.ToSelectQueryBlock();
repeatQueryBlock.SelectElements.Clear();
foreach (WSelectScalarExpression selectColumnExpr in secondSelectList)
{
repeatQueryBlock.SelectElements.Add(selectColumnExpr);
}
//Then we will use the inputVariableVistorMap to replace ColumnRefernceExpression in the syntax tree
//which matchs n_0.id to R_0.key_0 except for WPathTableReference
new ModifyRepeatInputVariablesVisitor().Invoke(repeatQueryBlock, inputVariableVistorMap);
new ModifyRepeatInputVariablesVisitor().Invoke(repeatConditionExpr, inputVariableVistorMap);
List <WScalarExpression> repeatParameters = new List <WScalarExpression>()
{
SqlUtil.GetScalarSubquery(SqlUtil.GetBinaryQueryExpr(firstQueryExpr, repeatQueryBlock)),
repeatConditionExpr
};
WSchemaObjectFunctionTableReference tableRef = SqlUtil.GetFunctionTableReference(GremlinKeyword.func.Repeat, repeatParameters, this.GetVariableName());
return(SqlUtil.GetCrossApplyTableReference(tableRef));
}