| 2013-08-20 20:18:02 |
Victor Choueiri |
description |
It seems that query's only return results of documents, where all the document's fields are indexed [regardless of whether or not those fields are being queried].
I've included a number of examples below, I hope they clarify the situation:
Examples:
Database definition:
U1db.Database {
id: theDB
path: "indextest.db"
}
Two sample documents: the first has only a "title" field, the second has both "title" and "num" fields:
U1db.Document {
database: theDB
create: true
docId: "vic"
defaults: {"title": "vic"}
}
U1db.Document {
database: theDB
create: true
docId: "xqwzts"
defaults: {
"title": "xqwzts",
"num": "123"
}
}
Index only the title field since it is what I care about querying:
U1db.Index {
database: theDB
id: theIndex
expression: ["title"]
}
An empty query which should match all documents in the index:
U1db.Query {
id: theQuery
index: theIndex
}
Expected result: both documents should be returned
Action result: only the first document is returned
Detailed output:
JSON.stringify(theDB.listDocs())
{"0":"vic","1":"xqwzts"}
JSON.stringify(theIndex)
{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"}}
Specifying the query to search for title = "*" makes no difference:
U1db.Query {
id: theQuery
index: theIndex
query: [{"title": "*"}]
}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"},"query":[{"title":"*"}]}
It seems the second document simply isn't in the index, so no query will return it.
To add the second document to the index we must add all fields of the document to the index expression:
U1db.Index {
database: theDB
id: theIndex
expression: ["title", "num"]
}
And remove the query clause to have the query return all documents in the index:
U1db.Query {
id: theQuery
index: theIndex
}
So now the output becomes:
JSON.stringify(theIndex)
{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"},{"num":"123"}],"documents":{"0":"vic","1":"xqwzts"}}
But now in order to add a query clause all the fields in the index which are also in the document have to be included.
U1db.Query {
id: theQuery
index: theIndex
query: [{"title": "*"}]
}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"},"query":[{"title":"*"}]}
In order to actually return all the documents with title=* we have to also specify that num=*
U1db.Query {
id: theQuery
index: theIndex
query: [{"title": "*"}, {"num": "*"}]
}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"},{"num":"123"}],"documents":{"0":"vic","1":"xqwzts"},"query":[{"title":"*"},{"num":"*"}]}
Conclusion:
- In order to be included in the index, ALL fields in a document must be included in the index's expression clause.
- In order to be returned by a query, ALL fields in a document [which are also in the index] must be included in the query's query clause.
This is pretty problematic with large/complicated documents where including every single field in the expression/query clause is not really feasible. |
It seems that queries only return results of documents, where all the document's fields are indexed [regardless of whether or not those fields are being queried].
I've included a number of examples below, I hope they clarify the situation:
Examples:
Database definition:
U1db.Database {
id: theDB
path: "indextest.db"
}
Two sample documents: the first has only a "title" field, the second has both "title" and "num" fields:
U1db.Document {
database: theDB
create: true
docId: "vic"
defaults: {"title": "vic"}
}
U1db.Document {
database: theDB
create: true
docId: "xqwzts"
defaults: {
"title": "xqwzts",
"num": "123"
}
}
Index only the title field since it is what I care about querying:
U1db.Index {
database: theDB
id: theIndex
expression: ["title"]
}
An empty query which should match all documents in the index:
U1db.Query {
id: theQuery
index: theIndex
}
Expected result: both documents should be returned
Action result: only the first document is returned
Detailed output:
JSON.stringify(theDB.listDocs())
{"0":"vic","1":"xqwzts"}
JSON.stringify(theIndex)
{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"}}
Specifying the query to search for title = "*" makes no difference:
U1db.Query {
id: theQuery
index: theIndex
query: [{"title": "*"}]
}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"},"query":[{"title":"*"}]}
It seems the second document simply isn't in the index, so no query will return it.
To add the second document to the index we must add all fields of the document to the index expression:
U1db.Index {
database: theDB
id: theIndex
expression: ["title", "num"]
}
And remove the query clause to have the query return all documents in the index:
U1db.Query {
id: theQuery
index: theIndex
}
So now the output becomes:
JSON.stringify(theIndex)
{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"},{"num":"123"}],"documents":{"0":"vic","1":"xqwzts"}}
But now in order to add a query clause all the fields in the index which are also in the document have to be included.
U1db.Query {
id: theQuery
index: theIndex
query: [{"title": "*"}]
}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"},"query":[{"title":"*"}]}
In order to actually return all the documents with title=* we have to also specify that num=*
U1db.Query {
id: theQuery
index: theIndex
query: [{"title": "*"}, {"num": "*"}]
}
JSON.stringify(theQuery)
{"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"},{"num":"123"}],"documents":{"0":"vic","1":"xqwzts"},"query":[{"title":"*"},{"num":"*"}]}
Conclusion:
- In order to be included in the index, ALL fields in a document must be included in the index's expression clause.
- In order to be returned by a query, ALL fields in a document [which are also in the index] must be included in the query's query clause.
This is pretty problematic with large/complicated documents where including every single field in the expression/query clause is not really feasible. |
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