1 files changed, 27 insertions, 0 deletions
diff --git a/app/services/help-service.ts b/app/services/help-service.ts
new file mode 100644
index 0000000..11bb4c0
--- /dev/null
+++ b/app/services/help-service.ts
@@ -0,0 +1,27 @@
+/// <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
+   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 <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": "scans all 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>.`
+}