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Improve Read Performance #107

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Improve Read Performance #107

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8 changes: 5 additions & 3 deletions lib/reader.js
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Original file line number Diff line number Diff line change
Expand Up @@ -42,14 +42,15 @@ class ParquetCursor {
this.columnList = columnList;
this.rowGroup = [];
this.rowGroupIndex = 0;
this.cursorIndex = 0;
}

/**
* Retrieve the next row from the cursor. Returns a row or NULL if the end
* of the file was reached
*/
async next() {
if (this.rowGroup.length === 0) {
if (this.cursorIndex >= this.rowGroup.length) {
if (this.rowGroupIndex >= this.metadata.row_groups.length) {
return null;
}
Expand All @@ -61,9 +62,10 @@ class ParquetCursor {

this.rowGroup = parquet_shredder.materializeRecords(this.schema, rowBuffer);
this.rowGroupIndex++;
this.cursorIndex = 0;
}

return this.rowGroup.shift();
return this.rowGroup[this.cursorIndex++];
}

/**
Expand Down Expand Up @@ -137,7 +139,7 @@ class ParquetReader {
columnList = columnList.map((x) => x.constructor === Array ? x : [x]);

return new ParquetCursor(
this.metadata,
this.metadata,
this.envelopeReader,
this.schema,
columnList);
Expand Down