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f1a3d8e14d
Added information in the "DOUBLE Data Type" (impala_double.html) and the "FLOAT Data Type" (impala_float.html) topics about how Impala handles NaN values. Change-Id: Id9485b6790d58fafdae32332d2634cbe893d7fb0 Reviewed-on: http://gerrit.cloudera.org:8080/7098 Reviewed-by: Michael Brown <mikeb@cloudera.com> Tested-by: Impala Public Jenkins
125 lines
4.6 KiB
XML
125 lines
4.6 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
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<concept id="float">
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<title>FLOAT Data Type</title>
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<titlealts audience="PDF"><navtitle>FLOAT</navtitle></titlealts>
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<prolog>
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<metadata>
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<data name="Category" value="Impala"/>
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<data name="Category" value="Impala Data Types"/>
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<data name="Category" value="SQL"/>
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<data name="Category" value="Data Analysts"/>
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<data name="Category" value="Developers"/>
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<data name="Category" value="Schemas"/>
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</metadata>
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</prolog>
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<conbody>
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<p>
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A single precision floating-point data type used in <codeph>CREATE TABLE</codeph> and <codeph>ALTER
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TABLE</codeph> statements.
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</p>
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<p conref="../shared/impala_common.xml#common/syntax_blurb"/>
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<p>
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In the column definition of a <codeph>CREATE TABLE</codeph> statement:
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</p>
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<codeblock><varname>column_name</varname> FLOAT</codeblock>
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<p>
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<b>Range:</b> 1.40129846432481707e-45 .. 3.40282346638528860e+38, positive or negative
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</p>
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<p>
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<b>Precision:</b> 6 to 9 significant digits, depending on usage. The number of significant digits does
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not depend on the position of the decimal point.
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</p>
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<p>
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<b>Representation:</b> The values are stored in 4 bytes, using
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<xref href="https://en.wikipedia.org/wiki/Single-precision_floating-point_format" scope="external" format="html">IEEE 754 Single Precision Binary Floating Point</xref> format.
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</p>
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<p>
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<b>Conversions:</b> Impala automatically converts <codeph>FLOAT</codeph> to more precise
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<codeph>DOUBLE</codeph> values, but not the other way around. You can use <codeph>CAST()</codeph> to convert
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<codeph>FLOAT</codeph> values to <codeph>TINYINT</codeph>, <codeph>SMALLINT</codeph>, <codeph>INT</codeph>,
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<codeph>BIGINT</codeph>, <codeph>STRING</codeph>, <codeph>TIMESTAMP</codeph>, or <codeph>BOOLEAN</codeph>.
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You can use exponential notation in <codeph>FLOAT</codeph> literals or when casting from
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<codeph>STRING</codeph>, for example <codeph>1.0e6</codeph> to represent one million.
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<ph conref="../shared/impala_common.xml#common/cast_int_to_timestamp"/>
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</p>
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<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
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<!--Below conref'd content fixes IMPALA-3603-->
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<p conref="../shared/impala_common.xml#common/how_impala_handles_nan_values"/>
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<codeblock>
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SELECT CAST('nan' AS FLOAT)=CAST('nan' AS FLOAT);
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</codeblock>
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<p conref="../shared/impala_common.xml#common/example_blurb"/>
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<codeblock>CREATE TABLE t1 (x FLOAT);
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SELECT CAST(1000.5 AS FLOAT);
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</codeblock>
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<p conref="../shared/impala_common.xml#common/partitioning_imprecise"/>
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<p conref="../shared/impala_common.xml#common/hbase_ok"/>
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<p conref="../shared/impala_common.xml#common/parquet_ok"/>
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<p conref="../shared/impala_common.xml#common/text_bulky"/>
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<!-- <p conref="../shared/impala_common.xml#common/compatibility_blurb"/> -->
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<p conref="../shared/impala_common.xml#common/internals_4_bytes"/>
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<!-- <p conref="../shared/impala_common.xml#common/added_in_20"/> -->
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<p conref="../shared/impala_common.xml#common/column_stats_constant"/>
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<p conref="../shared/impala_common.xml#common/restrictions_blurb"/>
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<!-- This conref appears under SUM(), AVG(), FLOAT, and DOUBLE topics. -->
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<p conref="../shared/impala_common.xml#common/sum_double"/>
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<p conref="../shared/impala_common.xml#common/float_double_decimal_caveat"/>
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<p conref="../shared/impala_common.xml#common/kudu_blurb"/>
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<p conref="../shared/impala_common.xml#common/kudu_non_pk_data_type"/>
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<p conref="../shared/impala_common.xml#common/related_info"/>
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<p>
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<xref href="impala_literals.xml#numeric_literals"/>, <xref href="impala_math_functions.xml#math_functions"/>,
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<xref href="impala_double.xml#double"/>
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</p>
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</conbody>
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</concept>
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