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Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com> Co-authored-by: luhuayi <luhuayi@huawei.com> Co-committed-by: luhuayi <luhuayi@huawei.com>
55 lines
5.5 KiB
HTML
55 lines
5.5 KiB
HTML
<a name="EN-US_TOPIC_0000001764650340"></a><a name="EN-US_TOPIC_0000001764650340"></a>
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<h1 class="topictitle1">PG_LARGEOBJECT</h1>
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<div id="body8662426"><p id="EN-US_TOPIC_0000001764650340__en-us_topic_0059777745_p181407189535"><strong id="EN-US_TOPIC_0000001764650340__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_0000001764650340__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_0000001764650340__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_0000001764650340__t0c2e2d209e2645d1856fdcbf968818cd" frame="border" border="1" rules="all"><caption><b>Table 1 </b>PG_LARGEOBJECT columns</caption><thead align="left"><tr id="EN-US_TOPIC_0000001764650340__ref1f8051abf6439f860e42d4d02a7464"><th align="left" class="cellrowborder" valign="top" width="14.29%" id="mcps1.3.3.2.5.1.1"><p id="EN-US_TOPIC_0000001764650340__af46d647e7a0b4e79b528f12bfef18482"><strong id="EN-US_TOPIC_0000001764650340__b471013391263">Column</strong></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_0000001764650340__a0e7fd0246605426e887e182ad70fa3f0"><strong id="EN-US_TOPIC_0000001764650340__b162231342152620">Type</strong></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_0000001764650340__a667f1a18fb91474b882be33ac354254a"><strong id="EN-US_TOPIC_0000001764650340__b10215194419261">Reference</strong></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_0000001764650340__a7a28e5d4d3874fa58ea541dcecf82472"><strong id="EN-US_TOPIC_0000001764650340__b1154446182619">Description</strong></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_0000001764650340__r58ab183d9d7a4bacb7598e3e9dc7d1ef"><td class="cellrowborder" valign="top" width="14.29%" headers="mcps1.3.3.2.5.1.1 "><p id="EN-US_TOPIC_0000001764650340__a76d9d58009e34a63be674f389d821bc3">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_0000001764650340__afdfacdddb6714154a7495eee4194ec5b">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_0000001764650340__acb75156289c045e9a151f8e2ff1e3263"><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_0000001764650340__aab26a6c570a14d01a88ad0b730b3474b">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_0000001764650340__r0d85e982b5aa4bd2a66b995c09b5b8bc"><td class="cellrowborder" valign="top" width="14.29%" headers="mcps1.3.3.2.5.1.1 "><p id="EN-US_TOPIC_0000001764650340__a7231592ffe5c47848626258ca955bedc">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_0000001764650340__a1c1a7041a5314e5ba284e2e58ebdf6ed">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_0000001764650340__aff3fc06e7ea54fe78f9fc3d91477e6ea">-</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_0000001764650340__abe8774a2c77f4782bd8b57ee627c831f">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_0000001764650340__re322808d8c444608a3cf999e08e3cb18"><td class="cellrowborder" valign="top" width="14.29%" headers="mcps1.3.3.2.5.1.1 "><p id="EN-US_TOPIC_0000001764650340__ab523236fb09942b1997a9379791a65c3">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_0000001764650340__a753c132507054b8a861b4bc89d0578d2">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_0000001764650340__a78cf0601277e49e58b523c457163cd9d">-</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_0000001764650340__aa453f4309b0a4fd1ba72355c1253b047">Actual data stored in the large object. This will never be more than <strong id="EN-US_TOPIC_0000001764650340__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_0000001764650340__aac6f7d68536943049e1de87f7b9935b3">Each row of <strong id="EN-US_TOPIC_0000001764650340__b10794104618272">pg_largeobject</strong> holds data for one page of a large object, beginning at byte offset (<strong id="EN-US_TOPIC_0000001764650340__b779434610277">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_0000001764650340__b842352706161329">LOBLKSIZE</strong> bytes even if they are not the last page of the object. Missing regions within a large object are read as 0.</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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