Repository: impala Updated Branches: refs/heads/master 52a2d90f9 -> 202807e2f
[DOCS] Minor copy edits and typo fixes Change-Id: I353a7917eb770aa40696476a587d7600289c336c Cherry-picks: not for 2.x. Reviewed-on: http://gerrit.cloudera.org:8080/10276 Reviewed-by: Alex Rodoni <arod...@cloudera.com> Tested-by: Alex Rodoni <arod...@cloudera.com> Project: http://git-wip-us.apache.org/repos/asf/impala/repo Commit: http://git-wip-us.apache.org/repos/asf/impala/commit/80d07aff Tree: http://git-wip-us.apache.org/repos/asf/impala/tree/80d07aff Diff: http://git-wip-us.apache.org/repos/asf/impala/diff/80d07aff Branch: refs/heads/master Commit: 80d07afff3ab03da77071198eb8c5181c01a215c Parents: 52a2d90 Author: Alex Rodoni <arod...@cloudera.com> Authored: Tue May 1 15:07:30 2018 -0700 Committer: Alex Rodoni <arod...@cloudera.com> Committed: Tue May 1 22:10:42 2018 +0000 ---------------------------------------------------------------------- docs/topics/impala_decimal.xml | 166 +++++++++++++++++------------------- 1 file changed, 78 insertions(+), 88 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/impala/blob/80d07aff/docs/topics/impala_decimal.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_decimal.xml b/docs/topics/impala_decimal.xml index f1a7f7a..268a789 100644 --- a/docs/topics/impala_decimal.xml +++ b/docs/topics/impala_decimal.xml @@ -208,20 +208,20 @@ under the License. </p> <p> - For all arithmetic options, the resulting precision is at most 38. + For all arithmetic operations, the resulting precision is at most 38. </p> <p> - If the precision of the result would be greater than 38, Impala truncates the result from - the back, but keeps at least 6 fractional digits in scale and rounds. + If the resulting precision would be greater than 38, Impala truncates the result from the + back, but keeps at least 6 fractional digits in scale and rounds. </p> <p> For example, <codeph>DECIMAL(38, 20) * DECIMAL(38, 20)</codeph> returns <codeph>DECIMAL(38, 6)</codeph>. According to the table below, the resulting precision and scale would be <codeph>(77, 40)</codeph>, but they are higher than the maximum precision - and scale. So, Impala sets the precision to the maximum allowed 38, and truncates the - scale to 6. + and scale for <codeph>DECIMAL</codeph>. So, Impala sets the precision to the maximum + allowed 38, and truncates the scale to 6. </p> <p> @@ -401,8 +401,7 @@ INSERT INTO flt SELECT CAST(1e37 AS DECIMAL(38, 0)); SELECT CAST(c AS DECIMAL(38, 0)) FROM flt; Result: 9999999933815812510711506376257961984</codeblock> - <p - dir="ltr"> + <p dir="ltr"> The result has a loss of information due to implicit casting. This is why we discourage using the <codeph>DOUBLE</codeph> and <codeph>FLOAT</codeph> types in general. @@ -426,7 +425,7 @@ Result: 9999999933815812510711506376257961984</codeblock> <li> Integer values can be implicitly converted to <codeph>DECIMAL</codeph> when there is - enough room in the <codeph>DECIMAL</codeph> to guarantee that all digits will fit. The + enough room in the <codeph>DECIMAL</codeph> to guarantee that all digits fit. The integer types require the following numbers of digits to the left of the decimal point when converted to <codeph>DECIMAL</codeph>: <ul> @@ -594,11 +593,8 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock> <ul> <li dir="ltr"> <p dir="ltr"> - If scale in <codeph>STRING</codeph> > scale in <codeph>DECIMAL</codeph>: - </p> - - <p dir="ltr"> - The fractional digits are rounded to the <codeph>DECIMAL</codeph> scale. + If scale in <codeph>STRING</codeph> > scale in <codeph>DECIMAL</codeph>, the + fractional digits are rounded to the <codeph>DECIMAL</codeph> scale. </p> <p dir="ltr"> @@ -724,17 +720,12 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock> <p conref="../shared/impala_common.xml#common/file_format_blurb"/> - <p> + <p dir="ltr"> + The <codeph>DECIMAL</codeph> data type can be stored in any of the file formats supported + by Impala. <ul> <li dir="ltr"> <p dir="ltr"> - The <codeph>DECIMAL</codeph> data type can be stored in any of the file formats - supported by Impala. - </p> - </li> - - <li dir="ltr"> - <p dir="ltr"> Impala can query Avro, RCFile, or SequenceFile tables that contain <codeph>DECIMAL</codeph> columns, created by other Hadoop components. </p> @@ -834,10 +825,10 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock> Although an <codeph>ALTER TABLE ... REPLACE COLUMNS</codeph> statement that changes the precision or scale of a <codeph>DECIMAL</codeph> column succeeds, any subsequent attempt to query the changed column results in a fatal error. - (The other columns can still be queried successfully.) This is because the - metadata about the columns is stored in the data files themselves, and - <codeph>ALTER TABLE</codeph> does not actually make any updates to the data - files. + This is because the metadata about the columns is stored in the data files + themselves, and <codeph>ALTER TABLE</codeph> does not actually make any updates + to the data files. The other unaltered columns can still be queried + successfully. </p> </li> @@ -870,102 +861,101 @@ INSERT INTO decimals_11_8 VALUES (CAST(1 AS TINYINT));</codeblock> STATS</codeph> statement. </p> - <p conref="../shared/impala_common.xml#common/compatibility_blurb"/> + <p> + <b>Compatibility with older version of DECIMAL:</b> + </p> <p> - <ul> - <li dir="ltr"> - <p dir="ltr"> - This version of <codeph>DECIMAL</codeph> type is the default in - <keyword keyref="impala30_full"/> and higher. The key differences between this - version of <codeph>DECIMAL</codeph> and the previous <codeph>DECIMAL</codeph> V1 in - Impala 2.x include the following. - </p> - <simpletable frame="all" relcolwidth="1* 1* 1*" - id="simpletable_bdr_rzc_qdb"> + This version of <codeph>DECIMAL</codeph> type is the default in + <keyword + keyref="impala30_full"/> and higher. The key differences between this + version of <codeph>DECIMAL</codeph> and the previous <codeph>DECIMAL</codeph> V1 in Impala + 2.x include the following. + </p> + + <p> + <simpletable frame="all" relcolwidth="1* 1* 1*" + id="simpletable_bwl_khm_rdb"> - <sthead> + <sthead> - <stentry/> + <stentry/> - <stentry>DECIMAL in <keyword keyref="impala30_full"/> or - higher</stentry> + <stentry>DECIMAL in <keyword keyref="impala30_full"/> or + higher</stentry> - <stentry>DECIMAL in <keyword keyref="impala212_full"/> or - lower + <stentry>DECIMAL in <keyword keyref="impala212_full"/> or lower + </stentry> - </stentry> + </sthead> - </sthead> + <strow> - <strow> + <stentry>Overall behavior</stentry> - <stentry>Overall behavior</stentry> + <stentry>Returns either the result or an error.</stentry> - <stentry>Returns either the result or an error.</stentry> + <stentry>Returns either the result or <codeph>NULL</codeph> with a + warning.</stentry> - <stentry>Returns either the result or <codeph>NULL</codeph> with a - warning.</stentry> + </strow> - </strow> + <strow> - <strow> + <stentry>Overflow behavior</stentry> - <stentry>Overflow behavior</stentry> + <stentry>Aborts with an error.</stentry> - <stentry>Aborts with an error.</stentry> + <stentry>Issues a warning and returns <codeph>NULL</codeph>.</stentry> - <stentry>Issues a warning and returns - <codeph>NULL</codeph>.</stentry> + </strow> - </strow> + <strow> - <strow> + <stentry>Truncation / rounding behavior in arithmetic</stentry> - <stentry>Truncation / rounding behavior in arithmetic</stentry> + <stentry>Truncates and rounds digits from the back.</stentry> - <stentry>Truncates and rounds digits from the back.</stentry> + <stentry>Truncates digits from the front.</stentry> - <stentry>Truncates digits from the front.</stentry> + </strow> - </strow> + <strow> - <strow> + <stentry>String cast</stentry> - <stentry>String cast</stentry> + <stentry>Truncates from the back and rounds.</stentry> - <stentry>Truncates from the back and rounds.</stentry> + <stentry>Truncates from the back.</stentry> - <stentry>Truncates from the back.</stentry> + </strow> - </strow> + </simpletable> + </p> - </simpletable> - <p> - If you need to continue using the first version of the <codeph>DECIMAL</codeph> type - for the backward compatibility of your queries, set the <codeph>DECIMAL_V2</codeph> - query option to <codeph>FALSE</codeph>: + <p> + If you need to continue using the first version of the <codeph>DECIMAL</codeph> type for + the backward compatibility of your queries, set the <codeph>DECIMAL_V2</codeph> query + option to <codeph>FALSE</codeph>: <codeblock>SET DECIMAL_V2=FALSE;</codeblock> - </p> - </li> + </p> - <li dir="ltr"> - <p dir="ltr"> - Use the <codeph>DECIMAL</codeph> data type in Impala for applications where you used - the <codeph>NUMBER</codeph> data type in Oracle. - </p> + <p> + <b>Compatibility with other databases:</b> + </p> - <p dir="ltr"> - The Impala <codeph>DECIMAL</codeph> type does not support the Oracle idioms of - <codeph>*</codeph> for scale. - </p> + <p dir="ltr"> + Use the <codeph>DECIMAL</codeph> data type in Impala for applications where you used the + <codeph>NUMBER</codeph> data type in Oracle. + </p> - <p dir="ltr"> - The Impala <codeph>DECIMAL</codeph> type does not support negative values for - precision. - </p> - </li> - </ul> + <p dir="ltr"> + The Impala <codeph>DECIMAL</codeph> type does not support the Oracle idioms of + <codeph>*</codeph> for scale. + </p> + + <p dir="ltr"> + The Impala <codeph>DECIMAL</codeph> type does not support negative values for precision. </p> </conbody>
