app/services/help-service.ts


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/// <reference path="lodash.d.ts" />

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
   trying 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 <strong>join key</strong>.`,
   "AGGREGATE": `groups records together based on a GROUP BY or aggregate function (like <code>sum()</code>).`,
   "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 <strong>Index</strong>. 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 <strong>Index</strong>. Index Only Scans perform a single read operation
   from the index and do not read from the corresponding table.`,
   "BITMAP HEAP SCAN": "searches through the pages returned by the <strong>Bitmap Index Scan</strong> for relevant rows.",
   "BITMAP INDEX SCAN": `uses a <strong>Bitmap Index</strong> (index which uses 1 bit per page) to find all relevant pages.
   Results of this node are fed to the <strong>Bitmap Heap Scan</strong>.`
}