///
export class HelpService {
getNodeTypeDescription(nodeType: string) {
return NODE_DESCRIPTIONS[nodeType.toUpperCase()];
}
}
export var NODE_DESCRIPTIONS = {
"LIMIT":"returns a specified number of rows from a record set.",
"SORT": "sorts a record set based on the specified sort key.",
"NESTED LOOP": `merges two record sets by looping through every record in the first set and
tries to find a match in the second set. All matching records are returned.`,
"MERGE JOIN": `merges two record sets by first sorting them on a join key.`,
"AGGREGATE": `groups records together based on a GROUP BY or aggregate function (like sum()
).`,
"HASHAGGREGATE": `groups records together based on a GROUP BY or aggregate function (like sum()). Hash Aggregate uses
a hash to first organize the records by a key.`,
"SEQ SCAN": `finds relevant records by sequentially scanning the table. Seq Scans perform a single read operation
(only the table is read).`,
"INDEX SCAN": `finds relevant records based on an Index. Index Scans perform 2 read operations: one to
read the index and another to read the actual value from the table.`,
"INDEX ONLY SCAN": `finds relevant records based on an Index. Index Only Scans perform a single read operation
from the index and do not read from the corresponding table.`,
"BITMAP HEAP SCAN": "scans all pages returned by the Bitmap Index Scan for relevant rows.",
"BITMAP INDEX SCAN": `uses a Bitmap Index (index which uses 1 bit per page) to find all relevant pages.
Results of this node are fed to the Bitmap Heap Scan.`
}