Joseph Doherty
0a5aa9fc43
Key-value and where-pair plans had no row limit, so a selector pointed at a history or events table materialised every matching row on every poll. ISqlDialect gains RowLimitPrefix/RowLimitSuffix(n) (SQL Server TOP (n), Postgres LIMIT n, Oracle FETCH FIRST n ROWS ONLY); plans carry a RowCap (distinct keys, or 1) and ask for RowCap+1 rows; the reader also stops client-side at RowCap+1. Getting the extra row proves the selector ambiguous: the group publishes BadConfigurationError with a rate-limited warning. The reader reports those answered refusals so the driver counts them as answer evidence, and any refusal-only poll now restores Healthy after a comms fault. Refs #744 Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
226 lines
12 KiB
C#
226 lines
12 KiB
C#
using System.Data.Common;
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using System.Globalization;
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using Microsoft.Data.SqlClient;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
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namespace ZB.MOM.WW.OtOpcUa.Driver.Sql;
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/// <summary>
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/// Microsoft SQL Server dialect (design §2.2) — the default provider. Bracket quoting,
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/// <c>INFORMATION_SCHEMA</c> catalog SQL, and the design §3.7 type-family map.
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/// <para>Stateless and immutable, so a single instance is safely shared by the driver's poll reader and
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/// the AdminUI browse session.</para>
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/// </summary>
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public sealed class SqlServerDialect : ISqlDialect
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{
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/// <summary>
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/// T-SQL's regular-identifier ceiling (<c>sysname</c> = <c>nvarchar(128)</c>). Enforced because a
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/// longer string cannot name a real catalog object — it is either a config mistake or padding, and
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/// rejecting it keeps the quoted output bounded.
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/// <para><b>The unit here is genuinely CHARACTERS</b> (UTF-16 code units, which is what
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/// <c>nvarchar(128)</c> counts), deliberately unlike <c>PostgresDialect</c> and <c>OracleDialect</c>,
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/// whose ceilings are byte limits in the database encoding. Measuring bytes here would reject a legal
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/// 128-character non-ASCII name.</para>
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/// </summary>
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internal const int MaxIdentifierLength = 128;
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/// <inheritdoc/>
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public SqlProvider Provider => SqlProvider.SqlServer;
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/// <inheritdoc/>
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public DbProviderFactory Factory => SqlClientFactory.Instance;
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// <summary>
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// T-SQL markers are <c>@</c>-prefixed — <c>ParameterMarker("k0")</c> is <c>"@k0"</c>.
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// </summary>
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// <param name="baseName">The bare base name.</param>
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// <returns>The <c>@</c>-prefixed marker.</returns>
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/// <inheritdoc />
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public string ParameterMarker(string baseName) => "@" + baseName;
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// <summary>
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// Identical to <see cref="ParameterMarker"/>: <c>Microsoft.Data.SqlClient</c> expects
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// <see cref="DbParameter.ParameterName"/> to carry the same <c>@</c> the statement does. (It also
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// accepts a bare name and prepends the <c>@</c> itself, but spelling it out keeps the parameter
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// collection readable in a profiler trace and matches what the SQL text says.)
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// </summary>
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// <param name="baseName">The bare base name.</param>
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// <returns>The <c>@</c>-prefixed bind name.</returns>
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/// <inheritdoc />
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public string ParameterBindName(string baseName) => "@" + baseName;
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// <summary>
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// No-op. <c>SqlCommand</c> binds by name out of the box, so there is nothing SQL Server needs set on a
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// fresh command — the member exists for Oracle's <c>BindByName</c> (see
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// <see cref="ISqlDialect.ConfigureCommand"/>).
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// </summary>
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// <param name="command">The command to configure; untouched here.</param>
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/// <inheritdoc />
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public void ConfigureCommand(DbCommand command)
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{
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// Intentionally empty: see the summary.
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}
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// <summary>
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// 2098 — SQL Server's hard cap is <b>2100 parameters per statement</b>, and
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// <c>Microsoft.Data.SqlClient</c> spends two of them itself: a parameterized command is executed
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// through <c>sp_executesql</c>, whose first two arguments are the statement text and the parameter
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// declaration list. A caller filling 2100 would therefore be rejected with
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// <c>"The incoming request has too many parameters"</c> for a limit it appeared to respect.
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// </summary>
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/// <inheritdoc />
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public int MaxBindParameters => 2098;
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/// <inheritdoc/>
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public string LivenessSql => "SELECT 1";
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// <summary>
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// T-SQL limits after the <c>SELECT</c> keyword, so the whole limit lives in the prefix —
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// <c>"TOP 1 "</c>, trailing space included so <c>SELECT TOP 1 [col]</c> composes with no extra
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// separator at the call site.
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// </summary>
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/// <inheritdoc />
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public string SingleRowLimitPrefix => "TOP 1 ";
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// <summary>Empty — T-SQL has no trailing row-limit clause (<c>OFFSET/FETCH</c> is a paging construct, not this).</summary>
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/// <inheritdoc />
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public string SingleRowLimitSuffix => string.Empty;
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/// <inheritdoc />
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// Parenthesised: TOP (n) is the documented modern form, and TOP n without parentheses is the
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// backwards-compatibility spelling.
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public string RowLimitPrefix(int rows)
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{
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ArgumentOutOfRangeException.ThrowIfLessThan(rows, 1);
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return "TOP (" + rows.ToString(System.Globalization.CultureInfo.InvariantCulture) + ") ";
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}
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/// <inheritdoc />
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public string RowLimitSuffix(int rows)
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{
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ArgumentOutOfRangeException.ThrowIfLessThan(rows, 1);
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return string.Empty;
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}
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/// <inheritdoc/>
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public string ListSchemasSql =>
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"SELECT DISTINCT TABLE_SCHEMA FROM INFORMATION_SCHEMA.TABLES ORDER BY TABLE_SCHEMA";
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// <summary>
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// <c>SCHEMA_NAME()</c> with no argument returns the calling principal's default schema — the one an
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// unqualified object name resolves in, which is precisely the question the catalog gate asks.
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// </summary>
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/// <inheritdoc />
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public string DefaultSchemaSql => "SELECT SCHEMA_NAME()";
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/// <inheritdoc/>
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public string ListTablesSql =>
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"SELECT TABLE_NAME, TABLE_TYPE FROM INFORMATION_SCHEMA.TABLES " +
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"WHERE TABLE_SCHEMA = @schema ORDER BY TABLE_NAME";
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/// <inheritdoc/>
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public string ListColumnsSql =>
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"SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE FROM INFORMATION_SCHEMA.COLUMNS " +
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"WHERE TABLE_SCHEMA = @schema AND TABLE_NAME = @table ORDER BY ORDINAL_POSITION";
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// <summary>
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// Brackets one identifier part, doubling any embedded <c>]</c> — the T-SQL escape rule, and the only
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// metacharacter that could terminate a bracketed identifier early. <c>[</c>, quotes, semicolons and
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// comment markers are inert inside brackets and are therefore passed through unchanged.
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// </summary>
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// <remarks>
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// <para><b>Rejects</b> (all as <see cref="ArgumentException"/>): null / empty / all-whitespace; longer
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// than <see cref="MaxIdentifierLength"/>; any control character (which covers embedded NUL, and the
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// C0/C1 ranges that can truncate or corrupt a logged/audited statement); and any Unicode
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// <see cref="System.Globalization.UnicodeCategory.Format"/> character — bidi overrides, zero-width
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// spaces, soft hyphen, BOM. Those last cannot escape the brackets, but they spoof the <em>rendered</em>
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// text of a log line or an AdminUI label while comparing byte-different from the real catalog name
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// (the Trojan-Source class, CVE-2021-42574) — the same log/audit-integrity concern that motivates the
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// control-character rule.</para>
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// <para>The rejection messages deliberately do <b>not</b> echo the offending value — it is untrusted
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// input and this exception's text reaches the driver log.</para>
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// <para><b>This is a backstop, not the only defence.</b> Design §8.1's catalog gate
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// (<c>SqlCatalogGate</c>) resolves an authored table/column against the live catalog at
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// Initialize and substitutes the catalog's own spelling, so on the poll path the value arriving here
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// is a string read back out of the catalog. The rules below still run — the gate uses them as its own
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// charset filter, and they must hold for any future caller that has no catalog to check against.</para>
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// </remarks>
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// <param name="ident">The bare, unquoted identifier part.</param>
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// <returns>The bracket-quoted identifier.</returns>
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// <exception cref="ArgumentException">The value cannot be a valid SQL Server identifier.</exception>
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/// <inheritdoc />
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public string QuoteIdentifier(string ident)
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{
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if (string.IsNullOrWhiteSpace(ident))
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throw new ArgumentException(
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"A SQL identifier must be a non-empty, non-whitespace name.", nameof(ident));
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if (ident.Length > MaxIdentifierLength)
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throw new ArgumentException(
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$"A SQL Server identifier may not exceed {MaxIdentifierLength} characters (got {ident.Length}).",
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nameof(ident));
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foreach (var ch in ident)
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{
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if (char.IsControl(ch))
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throw new ArgumentException(
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"A SQL identifier may not contain control characters (including NUL).", nameof(ident));
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// Cf is a *separate* category from Cc, so char.IsControl misses every bidi override and
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// zero-width character. They are inert inside brackets but spoof rendered log/UI text.
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if (CharUnicodeInfo.GetUnicodeCategory(ch) == UnicodeCategory.Format)
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throw new ArgumentException(
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"A SQL identifier may not contain Unicode format characters "
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+ "(bidi overrides, zero-width spaces, soft hyphen, BOM).", nameof(ident));
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}
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return string.Concat("[", ident.Replace("]", "]]", StringComparison.Ordinal), "]");
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}
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// <summary>
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// Folds an <c>INFORMATION_SCHEMA.COLUMNS.DATA_TYPE</c> family name onto a
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// <see cref="DriverDataType"/> per design §3.7.
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// </summary>
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// <remarks>
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// <para><b>Precision caveat:</b> <c>decimal</c> / <c>numeric</c> / <c>money</c> / <c>smallmoney</c>
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// collapse to <see cref="DriverDataType.Float64"/> in v1. A .NET <c>decimal</c> carries more
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// significant digits than a <c>double</c>, so a high-precision column (e.g. <c>decimal(38,10)</c>)
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// loses low-order digits. Authoring an explicit <c>"type": "String"</c> on the tag preserves the exact
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// textual value when that matters.</para>
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// <para><b>Fallback:</b> an unrecognised family maps to <see cref="DriverDataType.String"/> and never
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// throws — a schema browse must render a table containing an exotic column (<c>xml</c>,
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// <c>geography</c>, <c>hierarchyid</c>, <c>sql_variant</c>, a CLR UDT, <c>varbinary</c>) rather than
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// crash on it. Null/blank input takes the same fallback.</para>
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// <para><b>Deliberate non-mappings:</b> SQL Server's <c>timestamp</c>/<c>rowversion</c> is an opaque
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// 8-byte row version, <em>not</em> a date — it falls back to <see cref="DriverDataType.String"/>
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// rather than being mistaken for a <see cref="DriverDataType.DateTime"/>. <c>time</c> is a
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// time-of-day span, likewise not a point in time, and takes the same fallback.</para>
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// <para><c>tinyint</c> widens to <see cref="DriverDataType.Int16"/> (it is unsigned 0–255 in T-SQL, so
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// a signed 8-bit type would not hold it, and the driver type set has no <c>Byte</c>).</para>
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// </remarks>
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// <param name="sqlDataType">The bare SQL type family name; matched case-insensitively.</param>
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// <returns>The mapped driver data type, or <see cref="DriverDataType.String"/> when unrecognised.</returns>
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/// <inheritdoc />
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public DriverDataType MapColumnType(string sqlDataType)
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{
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if (string.IsNullOrWhiteSpace(sqlDataType)) return DriverDataType.String;
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return sqlDataType.Trim().ToLowerInvariant() switch
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{
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"bit" or "boolean" => DriverDataType.Boolean,
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"tinyint" or "smallint" => DriverDataType.Int16,
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"int" or "integer" => DriverDataType.Int32,
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"bigint" => DriverDataType.Int64,
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"real" => DriverDataType.Float32,
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"float" or "double" or "double precision"
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or "decimal" or "numeric" or "money" or "smallmoney" => DriverDataType.Float64,
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"char" or "nchar" or "varchar" or "nvarchar" or "text" or "ntext"
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or "uniqueidentifier" => DriverDataType.String,
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"date" or "datetime" or "datetime2" or "smalldatetime"
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or "datetimeoffset" => DriverDataType.DateTime,
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_ => DriverDataType.String,
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};
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}
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}
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