verticapy.vDataFrame.explain#

vDataFrame.explain(digraph: bool = False) → str#

Provides information on how Vertica is computing the current vDataFrame relation.

Parameters#

digraph: bool, optional: If set to True, returns only the digraph of the explain plan.

Returns#

str: explain plan

Examples#

Let’s begin by importing VerticaPy.

import verticapy as vp

Hint

By assigning an alias to verticapy, we mitigate the risk of code collisions with other libraries. This precaution is necessary because verticapy uses commonly known function names like “average” and “median”, which can potentially lead to naming conflicts. The use of an alias ensures that the functions from verticapy are used as intended without interfering with functions from other libraries.

Let us create a dummy dataset and check its Query Plan:

vdf = vp.vDataFrame({"val": [0, 10, 20]})

	123 val Integer 100%
1	0
2	10
3	20

We can display the Query Plan of the vDataFrame using:

print(vdf.explain())
------------------------------ 
QUERY PLAN DESCRIPTION: 

EXPLAIN SELECT /*+LABEL('vDataframe.explain')*/ * FROM ((SELECT 0 AS "val") UNION ALL (SELECT 10 AS "val") UNION ALL (SELECT 20 AS "val")) VERTICAPY_SUBTABLE

Access Path:
+-UNION ALL [Cost: 30, Rows: 3] (PATH ID: 8)
| +---> STORAGE ACCESS for dual [Cost: 10, Rows: 1] (PATH ID: 10)
| |      Projection: v_catalog.dual_p
| +---> STORAGE ACCESS for dual [Cost: 10, Rows: 1] (PATH ID: 12)
| |      Projection: v_catalog.dual_p
| +---> STORAGE ACCESS for dual [Cost: 10, Rows: 1] (PATH ID: 14)
| |      Projection: v_catalog.dual_p


----------------------------------------------- 
PLAN: BASE QUERY PLAN (GraphViz Format)
----------------------------------------------- 
digraph G {
graph [rankdir=BT, label = "BASE QUERY PLAN
	Query: EXPLAIN SELECT /*+LABEL(\'vDataframe.explain\')*/ * FROM ((SELECT 0 AS \"val\") UNION ALL (SELECT 10 AS \"val\") UNION ALL (SELECT 20 AS \"val\")) VERTICAPY_SUBTABLE
	
	All Nodes Vector: 
	
	  node[0]=v_demo_node0001 (initiator) Up
	", labelloc=t, labeljust=l ordering=out]
0[label = "Root 
	OutBlk=[UncTuple]", color = "green", shape = "house"];
1[label = "NewEENode 
	OutBlk=[UncTuple]", color = "green", shape = "box"];
2[label = "UnionAll
	Unc: Integer(8)", color = "green", shape = "box"];
3[label = "StorageUnionStep: dual_p
	RLE: Integer(8)", color = "purple", shape = "box"];
4[label = "ExprEval: 
	  0
	RLE: Integer(8)", color = "brown", shape = "box"];
5[label = "ScanStep: dual_p
	epoch (not emitted)", color = "brown", shape = "box"];
6[label = "StorageUnionStep: dual_p
	RLE: Integer(8)", color = "purple", shape = "box"];
7[label = "ExprEval: 
	  10
	RLE: Integer(8)", color = "brown", shape = "box"];
8[label = "ScanStep: dual_p
	epoch (not emitted)", color = "brown", shape = "box"];
9[label = "StorageUnionStep: dual_p
	RLE: Integer(8)", color = "purple", shape = "box"];
10[label = "ExprEval: 
	  20
	RLE: Integer(8)", color = "brown", shape = "box"];
11[label = "ScanStep: dual_p
	epoch (not emitted)", color = "brown", shape = "box"];
1->0 [label = "V[0]", color = "black"];
2->1 [label = "0", color = "blue"];
3->2 [label = "0", color = "blue"];
4->3 [label = "0", color = "blue"];
5->4 [label = "0", color = "blue"];
6->2 [label = "1", color = "blue"];
7->6 [label = "0", color = "blue"];
8->7 [label = "0", color = "blue"];
9->2 [label = "2", color = "blue"];
10->9 [label = "0", color = "blue"];
11->10 [label = "0", color = "blue"];}