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https://issues.apache.org/jira/browse/DRILL-799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14010655#comment-14010655
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Mehant Baid commented on DRILL-799:
-----------------------------------
The problem is we are using Math.pow() to adjust the scale of the input.
Math.pow() returns double which is imprecise and hence while multiplying it
with a large number (16 digit number in this case) it adds some noise to the
actual input. Instead of using Math.pow() we should move to a static list of
table containing powers of 10 we are interested in.
> cast bigint to decimal adds values after decimal points
> -------------------------------------------------------
>
> Key: DRILL-799
> URL: https://issues.apache.org/jira/browse/DRILL-799
> Project: Apache Drill
> Issue Type: Bug
> Components: Functions - Drill
> Reporter: Chun Chang
> Assignee: Mehant Baid
>
> tested use git.commit.id.abbrev=5d7e3d3
> when casting bigint, we add values after decimal points:
> 0: jdbc:drill:schema=dfs> select c_bigint, cast(c_bigint as decimal(18,2))
> from data where c_row = 9;
> +------------+------------+
> | c_bigint | EXPR$1 |
> +------------+------------+
> | -4567890123456789 | -4567890123456789.12 |
> +------------+------------+
> 0: jdbc:drill:schema=dfs> explain plan for select c_bigint, cast(c_bigint as
> decimal(18,2)) from data where c_row = 9;
> +------------+------------+
> | text | json |
> +------------+------------+
> | ScreenPrel
> ProjectPrel(c_bigint=[$2], EXPR$1=[CAST($2):DECIMAL(18, 2)])
> FilterPrel(condition=[=(CAST($1):INTEGER, 9)])
> ScanPrel(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath
> [path=maprfs:/user/root/mondrian/data]],
> selectionRoot=/user/root/mondrian/data, columns=[SchemaPath [`c_row`],
> SchemaPath [`c_bigint`]]]])
> | {
> "head" : {
> "version" : 1,
> "generator" : {
> "type" : "ExplainHandler",
> "info" : ""
> },
> "type" : "APACHE_DRILL_PHYSICAL",
> "options" : [ ],
> "resultMode" : "EXEC"
> },
> "graph" : [ {
> "pop" : "parquet-scan",
> "@id" : 1,
> "entries" : [ {
> "path" : "maprfs:/user/root/mondrian/data"
> } ],
> "storage" : {
> "type" : "file",
> "connection" : "maprfs:///",
> "workspaces" : {
> "default" : {
> "location" : "/user/root/mondrian/",
> "writable" : false,
> "storageformat" : null
> },
> "home" : {
> "location" : "/",
> "writable" : false,
> "storageformat" : null
> },
> "root" : {
> "location" : "/",
> "writable" : false,
> "storageformat" : null
> },
> "tmp" : {
> "location" : "/tmp",
> "writable" : true,
> "storageformat" : "csv"
> }
> },
> "formats" : {
> "psv" : {
> "type" : "text",
> "extensions" : [ "tbl" ],
> "delimiter" : "|"
> },
> "csv" : {
> "type" : "text",
> "extensions" : [ "csv" ],
> "delimiter" : ","
> },
> "tsv" : {
> "type" : "text",
> "extensions" : [ "tsv" ],
> "delimiter" : "\t"
> },
> "parquet" : {
> "type" : "parquet"
> },
> "json" : {
> "type" : "json"
> }
> }
> },
> "format" : {
> "type" : "parquet"
> },
> "columns" : [ "`c_row`", "`c_bigint`" ],
> "selectionRoot" : "/user/root/mondrian/data"
> }, {
> "pop" : "filter",
> "@id" : 2,
> "child" : 1,
> "expr" : "equal(cast( (`c_row` ) as INT ), 9) ",
> "initialAllocation" : 1000000,
> "maxAllocation" : 10000000000
> }, {
> "pop" : "project",
> "@id" : 3,
> "exprs" : [ {
> "ref" : "`c_bigint`",
> "expr" : "`c_bigint`"
> }, {
> "ref" : "`EXPR$1`",
> "expr" : "cast( (`c_bigint` ) as DECIMAL18(18, 2) )"
> } ],
> "child" : 2,
> "initialAllocation" : 1000000,
> "maxAllocation" : 10000000000
> }, {
> "pop" : "screen",
> "@id" : 4,
> "child" : 3,
> "initialAllocation" : 1000000,
> "maxAllocation" : 10000000000
> } ]
> } |
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