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Lu, Huayi
e6fa411af0
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com> Co-authored-by: Lu, Huayi <luhuayi@huawei.com> Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
55 lines
5.3 KiB
HTML
55 lines
5.3 KiB
HTML
<a name="EN-US_TOPIC_0000001188642216"></a><a name="EN-US_TOPIC_0000001188642216"></a>
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<h1 class="topictitle1">PG_LARGEOBJECT</h1>
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<div id="body8662426"><p id="EN-US_TOPIC_0000001188642216__en-us_topic_0059777745_p181407189535"><strong id="EN-US_TOPIC_0000001188642216__b46114391331">PG_LARGEOBJECT</strong> records the data making up large objects A large object is identified by an OID assigned when it is created. Each large object is broken into segments or "pages" small enough to be conveniently stored as rows in <strong id="EN-US_TOPIC_0000001188642216__b84235270616345">pg_largeobject</strong>. The amount of data per page is defined to be LOBLKSIZE (which is currently BLCKSZ/4, or typically 2 kB). </p>
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<p id="EN-US_TOPIC_0000001188642216__p1319074194317">It is accessible only to users with system administrator rights.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" id="EN-US_TOPIC_0000001188642216__td1fda183fa794af9b075f9ecb56ad423" frame="border" border="1" rules="all"><caption><b>Table 1 </b>PG_LARGEOBJECT columns</caption><thead align="left"><tr id="EN-US_TOPIC_0000001188642216__r5580e65ada57431d89c3e10c378d3ffe"><th align="left" class="cellrowborder" valign="top" width="14.29%" id="mcps1.3.3.2.5.1.1"><p id="EN-US_TOPIC_0000001188642216__a4830519f1cff46288ce1b22e90eb0d15">Name</p>
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</th>
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<th align="left" class="cellrowborder" valign="top" width="12.78%" id="mcps1.3.3.2.5.1.2"><p id="EN-US_TOPIC_0000001188642216__a8ad15555f5ee423985ba9a654dc5430c">Type</p>
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</th>
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<th align="left" class="cellrowborder" valign="top" width="30.45%" id="mcps1.3.3.2.5.1.3"><p id="EN-US_TOPIC_0000001188642216__ad6b89082b56d44379fa8afb72035ab01">Reference</p>
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</th>
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<th align="left" class="cellrowborder" valign="top" width="42.480000000000004%" id="mcps1.3.3.2.5.1.4"><p id="EN-US_TOPIC_0000001188642216__a7f8f5b6fbc7849da9a3fe4bd652bdea5">Description</p>
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</th>
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</tr>
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</thead>
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<tbody><tr id="EN-US_TOPIC_0000001188642216__rf1bd51dc7c134d50b6dd6a7b451c299b"><td class="cellrowborder" valign="top" width="14.29%" headers="mcps1.3.3.2.5.1.1 "><p id="EN-US_TOPIC_0000001188642216__a1156dfec393c4ab7b9cc15266dbd84ab">loid</p>
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</td>
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<td class="cellrowborder" valign="top" width="12.78%" headers="mcps1.3.3.2.5.1.2 "><p id="EN-US_TOPIC_0000001188642216__aeefcdbff6df24cf8b9e777b5e9ad7c43">oid</p>
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</td>
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<td class="cellrowborder" valign="top" width="30.45%" headers="mcps1.3.3.2.5.1.3 "><p id="EN-US_TOPIC_0000001188642216__a241879cb32b240e394b5bb1da0637833"><a href="dws_04_0599.html">PG_LARGEOBJECT_METADATA</a>.oid</p>
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</td>
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<td class="cellrowborder" valign="top" width="42.480000000000004%" headers="mcps1.3.3.2.5.1.4 "><p id="EN-US_TOPIC_0000001188642216__aacb0dd5bc7c942109d31f5d7e960a320">Identifier of the large object that includes this page</p>
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</td>
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</tr>
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<tr id="EN-US_TOPIC_0000001188642216__r566dab542f054998ac1787f558ea3293"><td class="cellrowborder" valign="top" width="14.29%" headers="mcps1.3.3.2.5.1.1 "><p id="EN-US_TOPIC_0000001188642216__aaa4a31b952b24f52bc4478ceecf29f97">pageno</p>
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</td>
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<td class="cellrowborder" valign="top" width="12.78%" headers="mcps1.3.3.2.5.1.2 "><p id="EN-US_TOPIC_0000001188642216__a0b6ed4b286734582b4c1411c784dabbf">integer</p>
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</td>
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<td class="cellrowborder" valign="top" width="30.45%" headers="mcps1.3.3.2.5.1.3 "><p id="EN-US_TOPIC_0000001188642216__aeb2f919865614dd8ace02d64977e308c">-</p>
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</td>
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<td class="cellrowborder" valign="top" width="42.480000000000004%" headers="mcps1.3.3.2.5.1.4 "><p id="EN-US_TOPIC_0000001188642216__a6c4c3936a8b9449ea29debaa24db5c21">Page number of this page within its large object (counting from zero)</p>
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</td>
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</tr>
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<tr id="EN-US_TOPIC_0000001188642216__r01e82271a0c440b6ad4427033b665be8"><td class="cellrowborder" valign="top" width="14.29%" headers="mcps1.3.3.2.5.1.1 "><p id="EN-US_TOPIC_0000001188642216__a75a15f4dbf4b4e7880671223bdb7f9f1">data</p>
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</td>
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<td class="cellrowborder" valign="top" width="12.78%" headers="mcps1.3.3.2.5.1.2 "><p id="EN-US_TOPIC_0000001188642216__a62d1b17ccae146f7ac2e7bda199498ec">bytea</p>
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</td>
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<td class="cellrowborder" valign="top" width="30.45%" headers="mcps1.3.3.2.5.1.3 "><p id="EN-US_TOPIC_0000001188642216__ac8972b13cfeb46b6bfa88e96d30b7544">-</p>
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</td>
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<td class="cellrowborder" valign="top" width="42.480000000000004%" headers="mcps1.3.3.2.5.1.4 "><p id="EN-US_TOPIC_0000001188642216__a8924313f387540b0b633799da7b535b7">Actual data stored in the large object. This will never be more than <strong id="EN-US_TOPIC_0000001188642216__b842352706161010">LOBLKSIZE</strong> bytes and might be less.</p>
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</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p id="EN-US_TOPIC_0000001188642216__a08e4f5db4a3b451abdeca9c777f0c344">Each row of <strong id="EN-US_TOPIC_0000001188642216__b842352706161039">pg_largeobject</strong> holds data for one page of a large object, beginning at byte offset (<strong id="EN-US_TOPIC_0000001188642216__b842352706161053">pageno * LOBLKSIZE</strong>) within the object. The implementation allows sparse storage: pages might be missing, and might be shorter than <strong id="EN-US_TOPIC_0000001188642216__b842352706161329">LOBLKSIZE</strong> bytes even if they are not the last page of the object. Missing regions within a large object are read as zeroes.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_04_0561.html">System Catalogs</a></div>
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</div>
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</div>
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