Extract execution plan in XML format to table - sql-server

Question

I'm trying to extract the data from SQL server execution plans in a generic way.
As an example the execution plan for
SELECT *
FROM sys.all_objects o1
as shown in SSMS is below
The UI shows nodes along with costs for each node and percentages. How can I extract this from the underlying XML into a table structure?
I've tried to query the XML by my self, but it seems that the XML structure is changing from query to query.

Answer 1

This should get you started (DB Fiddle example).
DECLARE #X XML = N'<?xml version="1.0" encoding="utf-16"?><ShowPlanXML ...';
DECLARE #Nodes TABLE
(
PlanId INT,
NodeId INT,
PhysicalOp VARCHAR(200),
EstimatedTotalSubtreeCost FLOAT,
EstimatedOperatorCost FLOAT,
ParentNodeId INT NULL,
PRIMARY KEY(PlanId, NodeId)
);
WITH XMLNAMESPACES (default 'http://schemas.microsoft.com/sqlserver/2004/07/showplan'),
plans AS
(
SELECT ROW_NUMBER() over (order by qp) as PlanId, qp.query('.') as plan_xml
FROM #X.nodes('//QueryPlan') n(qp)
)
INSERT #Nodes(PlanId, NodeId, PhysicalOp, EstimatedTotalSubtreeCost, ParentNodeId)
SELECT PlanId,
NodeId = relop.value('#NodeId', 'int'),
PhysicalOp = relop.value('#PhysicalOp', 'varchar(200)'),
EstimatedTotalSubtreeCost = relop.value('#EstimatedTotalSubtreeCost', 'float'),
/*XPath ancestor axis not supported so just go up a few levels and look for the closest ancestor Relop*/
ParentNodeId = COALESCE(
relop.value('..[local-name() = "RelOp"]/#NodeId', 'int'),
relop.value('../..[local-name() = "RelOp"]/#NodeId', 'int'),
relop.value('../../..[local-name() = "RelOp"]/#NodeId', 'int'),
relop.value('../../../..[local-name() = "RelOp"]/#NodeId', 'int')
)
FROM plans
CROSS APPLY plan_xml.nodes('//RelOp') n(relop);
UPDATE N1
SET EstimatedOperatorCost = EstimatedTotalSubtreeCost - ISNULL((SELECT SUM(EstimatedTotalSubtreeCost) FROM #Nodes N2 WHERE N1.PlanId = N2.PlanId AND N2.ParentNodeId = N1.NodeId),0)
FROM #Nodes N1
SELECT *,
EstPctOperatorCost = FORMAT(EstimatedOperatorCost/MAX(EstimatedTotalSubtreeCost) OVER (PARTITION BY PlanId), 'P0')
FROM #Nodes
The execution plan is a tree - there are likely more elegant ways of getting the parent operator than my attempt!
The above is not battle tested across a sample size of more than two execution plans so you may well encounter issues with it that you will need to fix.
You can visit the URI http://schemas.microsoft.com/sqlserver/2004/07/showplan to see information about the various schemas though for some reason I've never got to the bottom of it displays "The request is blocked." for me unless I use incognito mode.